An Ultimate Combo (or simply Ultimate) is a special finishing sequence that can be performed when the opponent's last health bar is in the "danger" state. This causes the winner to kill their opponent in a cinematic way, rather than simply besting them. Ultimate Combos are similar to Mortal Kombat series' system of fatalities, albeit lacking the overt gore and violent results as found in the aforementioned series. Also unlike MK's finishers, the Ultimates of KI are always performed as a finishing sequence to a combo rather than as independent command moves.
Description & Execution
In each Killer Instinct game, the player and their opponent are given two life bars. Once the last of these life bars is almost depleted a character will enter into the "danger" state, which is represented by its remaining life flashing a bright red and the background music changing to a shorter, intenser version of the track that is currently playing. While in this "danger" state the character's defeat is imminent, and they are at risk of being struck by either an Ultimate Combo or Ultra Combo. If the winning player is still in their first life bar, they can then attempt to unleash an Ultimate upon the almost defeated opponent as a finishing sequence to a regular combo.
In the original Killer Instinct, the "No Mercy" moves are executed more or less similarly to "Mortal Kombat's" fatalities: when placed into the "danger" stage, characters are additionally left dazed and will be temporarily defenseless. With their opponent stunned, the winner then can execute a "No Mercy" attack that causes them to finish off their adversary and kill them outright. These "No Mercy" moves are unique to the original KI 1994 game, and did not return either for the 1996 sequel of Killer Instinct 2 or for Killer Instinct (2013). In the latter two games, the No Mercy moves were replaced by the current system of Ultimate Combos, or Ultimates for short.
From Killer Instinct 2 onwards, Ultimate Combos supersede the anterior No Mercy moves. Killer Instinct players instead perform a killing blow by linking an Ultimate to a regular combo as its finishing sequence while their opponent is in the "danger" state. In Killer Instinct (2013), Ultimate Combos can additionally be performed even when the opponent isn't in "danger" state yet, but the Ultimate will then serve as a high-damage combo ender rather than a mortal strike. If the Ultimate Combo is performed while the other player is in the "danger" state, however, it will still function as a killing blow and finish off the opponent.
Shadow Jago was the first character in Killer Instinct (2013) to receive an Ultimate. Originally, it was exclusive to his boss version, but following the Killer Instinct Community Fund the playable Shadow Jago could use it as well. It can only be performed when Shadow Jago is still on his first life bar, and it is executed by inputting the command for Annihilation (QCF+LP+LK) during a combo when the target is in "danger" state. Initially, Iron Galaxy conveyed that they had no plans to give any other characters Ultimate Combos, but as of January 3rd, 2017, Jago was revealed to have been given his own Ultimate as well. However only 15 characters will be receiving an Ultimate this year (excluding Shadow Jago who already has Ultimate in a first place). As for now, only 5 characters will received an Ultimate starting in February 14, 2017.
The first five Ultimates known as the Ultimates Master Pack includes Ultimates for Jago, Thunder, TJ Combo, Maya & Tusk, and the second five known as the Ultimates Ultra Pack includes Ultimates for Fulgore, Sadira, Riptor, ARIA & Kilgore which will be released on May 2, 2017. The third and final five Ultimates known as the Ultimates Monster Pack were revealed in their in-game command list in which includes Ultimates for Sabrewulf, Glacius, Aganos, Hisako & Mira.  
Unlike Shadow Jago where you have to perform his Ultimate during the "danger" state, others must perform during the "Ultra Combo" state then quickly press (LP+LK) to trigger Ultimate.
List of No Mercy/Ultimate Combos
Killer Instinct (1994) - No Mercy Moves
- Sword Stab (Back-Forward-Forward+QP, Close) - Jago slashes across his opponent with his katana twice before stabbing them through the chest
- Falling Car (Back-Back-Forward-Forward+MP, Distant) - Jago begins to meditate and uses telekinesis to drop a car on his opponent
- Frog Stomp (Down-Back-Forward+QK, Close) - Orchid hits the opponent with her escrima, transforming them into a large toad. If the player presses forward kick (FK), she then jumps on it, squishing it
- Heart Attack (Back-Forward-Forward+QP, Close) - Orchid unzips her leotard and flashes her breasts at the opponent, causing them to have a heart attack and die. If the opponent is another Orchid, they instead throw their escrima and stomp their heels in jealousy
- Gun 'em Down (Half-circle-Forward+FK, Distant) - Fulgore turns his head into an automated turret that guns his opponent down
- Eye Laser (Half-circle-Back+FP, Distant) - Fulgore fires a salvo of red lasers from his eyes at his opponent
- Rain Dance (Half-circle-Forward+FP, Distant) - Thunder performs a short tribal dance, calling a bolt of lightning to strike his opponent
- Axe Uppercut (Half-circle-Back+FK, Close) - Thunder charges up his tomahawks before uppercutting his opponent away
- Lava Pool (Back-Back-Back+MP, Distant) - Cinder creates a pool of lava beneath his opponent that quickly melts them away
- Meltdown (Half-circle-Forward+QK, Distant) - Cinder performs his Inferno move, burning his opponent into a pile of ashes
- Skeleton Grab (Back-Back-Back+MK, Distant) - Spinal summons a skeleton from the ground beneath the opponent that drags them down underground
- Shield Stab (Back-Back-Forward+QK, Close) - Spinal slashes the opponent twice before stabbing them violently with the spike on his shield three times
- Ice Pick (Half-circle-Forward+MP, Distant) - Glacius stabs his opponent with his ice lance arm, freezing them solid
- Blob Engulf (Half-circle-Back+MK, Distant) - Glacius transforms into a bubble of water that surrounds the opponent and crushes them
- Acid Puddle (Back-Back-Back+FK, Distant) - Glacius melts into a puddle that absorbs his opponent
- Claw Stab (Back-Back+MK, Close) - Sabrewulf enlarges his claws and slashes the opponent in the stomach
- Screen Punch (Back-Back-Forward+MP, Distant) - Sabrewulf strikes the opponent from behind, causing them to fly towards the screen and smash into it
- Chiropractor (Back-Forward-Forward+MK, Close) - Combo punches his opponent to disorient them, then swiftly breaks their neck
- Screen Punch (Half-circle-Forward+FK, Close) - Combo punches the opponent from behind, causing them to fly towards the screen and smash into it
- Tail Stab (Forward-Forward-Back+FK, Distant) - Riptor stabs through the opponent with her tail
- Eat Opponent (Half-circle-Forward+MP, Close) - Riptor leaps towards the opponent and the screen blacks out - when the screen returns, Riptor is shown lying on the ground with an enlarged belly, having devoured the opponent
- Deadly Venom (Back-Back-Back+MK, Distant) - Riptor spits some form of acid or venom at the opponent's face that quickly kills them
Killer Instinct 2 - Ultimate Combos
- Jago throws a supercharged Endokuken that hits the opponent multiple times before exploding and incinerating them
- Jago spins around and throws a katana made of energy into his opponent
- Glacius grabs his opponent and freezes them over, then shatters them
- Glacius creates a lance out of ice and throws it into his opponent
- Tusk summons a meteor shower that ends with one giant meteor crushing the opponent
- Tusk summons a large reptilian creature to devour the opponent
- Spinal summons two giant hands to hold the opponent in place while a giant skull falls from above and crushes them
- Spinal levitates the opponent into the air and breaks their neck
- Kim Wu throws a shuriken star that explodes and incinerates the opponent
- Kim Wu, unsure of what to do, simply jumps on top of the opponent and knocks them over
- Sabrewulf summons bats that carry the opponent away and reduce them to raining blood and gore
- Sabrewulf fires a stream of electricity from his cyborg arms that incinerates the opponent
- Maya fires some short of shrink ray from the jewel on her headband, reducing the opponent to the size of a mouse
- Maya summons an elephant that falls on top of the opponent
- Fulgore presses a button on his arm, causing a massive laser to strike down from above and reduce his opponent to ashes
- Fulgore morphs into a larger, more armored form of himself with machine guns and guns down the opponent
- Orchid fires a stream of electricity from her tonfas that incinerates the opponent
- Orchid transforms into a Firecat and runs through the opponent, incinerating them (Only in "KI Gold")
- Combo takes out a sub-machine gun and guns the opponent down
- Combo uppercuts his opponent into the air so hard they never come back down
Killer Instinct (2013) - Ultimates
- Jago pulls out his sword and strikes his defeated opponent as the third hit launches the victim in the air; while the victim is still in the air, he too jumps into the air and then punch his victim to the ground; then Jago increases his fiery energy and then throws his enormous Endokuken towards the victim for the final blow, causing the screen to go white; the screen fades back to normal showing the victim engulfed in flames, then the smoke clears out as Jago landed to the ground before folding his arms looking down towards his defeated victim.
- Confirmed in Ultimates Monster Pack
- Confirmed in Ultimates Monster Pack
- Thunder calls the lightning, which strucks his tomahawks, then he spiritually dashes, which causes him to vanish as numerous of crows flying towards the defeated opponent; and he appears right before his defeated opponent's eyes. He then headbutts his defeated opponent and grabs the victim with his tomahawks and slams the victim to the ground; he then flips into the air, and stomps the victim as lightning struck fiercely onto the victim for the final blow.
- Sadira somersault kicks her defeated opponent into the air, then throws her daggers towards the victim, which causes the daggers to turn into a cobweb — leaving the victim to be trap onto the web; Sadira climbs down from the web to prey on her helpless victim, then Sadira slit her victim's throat with her dagger bracelet with a single swipe before spinning back onto the web staring at her deceased victim.
- Fulgore types his arm, and kicks his defeated opponent at a far distance; then he flies into the air, open his chest, charges up to the maximum and delivers a massive Devestation Beam down towards his victim, and the victim disintegrates causing the screen to go white due to the overheat of the Devastation Beam; Fulgore then lands back to ground and stands his position victorious.
- Shadow Jago slashes through his defeated victim back and forth thirteen times, then uppercuts the victim into the air; pulls his broadsword back out reversing the grip and strike the victim's body through in the air; as landing, Shadow Jago then strikes his broadsword onto the victim for the final kill before putting the weapon away.
- When Ultimate Master Pack 1 was released in February 14, 2017, his Season 1 boss version has Jago's Ultimate as well.
- Combo pounds his fists together, then he dashes towards his defeated opponent and strikes the victim three times; he then fatally straight-hooked his victim far away as a fatal knockout blow before the victim fatally collapses; then the bell rings as Combo walks away victorious.
- Maya backflips away from the defeated opponent and her daggers afloats out of her hands, then the daggers strikes the victim five times before merging together; then Maya flips into the air and the merging daggers strikes the stunned victim from behind before the daggers separates aiming towards the victim's head, then Maya, still in the air, flips down onto the victim, causing the victim's head to be slammed into the daggers, which instantly kills the victim; then the daggers returns back into Maya's hands.
- Riptor launches the defeated opponent into the air with her tail and as the victim is high above, she then flips over the victim and tries to bite their torso but misses by an inch; the victim lands lifelessly as Riptor lands on her back and breathes out fire in frustration; Riptor then looks at her victim — who is still alive by a hand twitch — before breathing fire onto the victim causing the screen to go white; the screen fades back to Riptor walking towards the flames where the cremated victim once lay before lying down next to the flames for a victory nap.
- Confirmed in Ultimates Monster Pack
- Confirmed in Ultimates Monster Pack
- ARIA disappears leaving her three drones to fly in seperate directions; the bass drone shoots the defeated victim with the sonic energy, then the blade drone launches the victim into the air, then the booster drone struck the aerial victim; then the drones flies together and then equipped as one, which causes ARIA to reappear with all her drones as she flies towards the victim and fiercefully struck her victim with her blade drone, causing the screen to go white; the screen fades back to ARIA, who is victorious after terminating her long-gone victim before looking back towards the screen.
- Tusk jumps into the air and slams his greatsword to the ground, causing the entire area to be covered in flames; Tusk dashes towards his defeated opponent, then strikes the victim four times; as a fifth and final strike, he impales his victim with his greatsword, instantly killing the victim; and then removes his weapon out of his victim, who collapses upon removal; Tusk then sticks his greatsword to the ground as victorious as the area are still covered in flames.
- Confirmed in Ultimates Monster Pack
- Kilgore opens his chest and launches a missile in the air, then filps over the defeated opponent as the defeated opponent looks at a flying missile, which flies back down aiming towards the defeated opponent; Kilgore appears from behind the defeated opponent to grab a hold of the victim as the missile is flying closer towards both Kilgore and the victim, Kilgore's chain guns begins to overheat while the victim is still struggling and staring at the missile at a final moment, Kilgore then explodes on the victim causing the victim to launch forward towards the missile, which explodes at a direct hit on the victim — instantly killing the victim and causing the screen to go white; the screen fades back to Kilgore, who is broken down from the explosion and covered in statics, but then automatically repair himself back in one piece in a sitting position.
- So far in KI 2013, Orchid, Spinal, Kan-Ra, Omen, Cinder, Kim Wu, Gargos, Eyedol, Shin Hisako, and the unannounced final Post-Season 3 character, along with guest characters Rash, Arbiter, and General RAAM, are the only characters not confirmed to have Ultimates.
- In KI 2013, some Ultimate animations are similar to existing moves:
- Ultimates - Official announcement by Iron Galaxy on Ultimates in KI 2013
- Exhibition of Killer Instinct (1994) "No Mercy" finishers
- Exhibition of Killer Instinct 2 Ultimate Combos for every character
- First Six Ultimates - Exhibition of the first six Ultimates in KI 2013 (Jago, Thunder, TJ Combo, Maya, Tusk & Shadow Jago)