In the Mortal Kombat series of fighting games, a Fatality is a special finishing move that can be used against one's opponent at the end of the final match. When the announcer says "Finish Him" or "Finish Her" if the opponent is female, the player can choose to kill him or her through a fatality move. If input correctly, the background will darken, followed by the desired result.
Unlike special moves, a Fatality may require certain distances and quick button sequences in order to achieve the desired result. For example, in Mortal Kombat 3, one of Sub-Zero's Fatalities requires that he stands close to the opponent and quickly execute Block, Block, Run, Block, Run. Every character has their own special Fatality that must be performed at a certain distance from the opponent. The number of Fatalities varies depending on the game; while characters in Mortal Kombat and Mortal Kombat: Deadly Alliance had only one, Mortal Kombat 3 and its updates featured as many as four.
Fatality-style finishing moves have also appeared in other fighting games from Midway (Killer Instinct, War Gods, Bio F.R.E.A.K.S., Mace: The Dark Age), and other companies (Blood Warrior/Ooedo Fight, Tattoo Assassins, Deadliest Warrior: The Game, Way of the Warrior, Primal Rage), though they are not named as such usually.
With Street Fighter II dominating arcades, Mortal Kombat co-creators Ed Boon and John Tobias wanted to create a fighting game that retained Street Fighter's gameplay without being a complete copy. Originally, the project revolved around actor Jean Claude Van Damme; this idea was eventually dropped and Mortal Kombat was born.
Tobias and Boon started with Street Fighter II's system and retained many of its conventions (fireball-style projectile attacks, one on one matches, minigames, etc.), but tweaked others (the block button, special endurance matches, juggling, etc.). The most notable additions were graphic blood and Fatality finishing moves. Traditional fighting games ends with the loser knocked unconscious and the victor posing for the players; characters never died during a match. The idea of a Fatality proved very popular with fans.
While creating Mortal Kombat, Ed Boon and John Tobias started with the idea of Street Fighter II-like system and retained many of its conventions, but tweaked others. The most notable additions were graphic blood effects, more brutal fighting techniques, and especially the fatal finishing moves (this was a novelty as the traditional fighting games ended with the loser simply knocked unconscious and the victor posing for the players).
According to Boon, "it started with an idea to enable the player to hit a dizzied opponent at the end of the match with a "free hit", and that idea "quickly evolved into something nasty". According to Tobias: "Our first idea was to use them as a finishing move for the final boss, Shang Tsung, who was going to pull out his sword and behead his opponent. Then we thought, What if the player could do that to his opponent?" When we watched players react to the Fatalities, we knew we had no choice but to give them more."
Mortal Kombat attracted numerous fans because it featured blood and the ability to perform Fatalities. The new feature addition helped make Mortal Kombat a successful game franchise that challenged the supremacy of Street Fighter II.
The Fatality concept caused considerable controversy, and many parents disapproved of the violence and the brutal endings of the game, deeming it disturbing.
The newly-founded ESRB gave Mortal Kombat a rating of M, deeming the game too violent for audiences under the age of 17. It's worth noting that, in the United States, the ESRB has no legal standing to prevent the sale of video games to minors, and therefore many people under the suggested age were able to play the game. Arcade owners were asked to monitor the ages of players, although few did.
Mortal Kombat II added some extras when it came to Fatalities. The characters were given two Fatalities each, and the Fatalities were more violent. Many angry parents and protesters wrote letters and complained about the content of the game, but since the ESRB had already rated the games, nothing came of the protests.
Many parents feared that the introduction of Fatalities would influence children to murder, and to teach them that it was okay to kill their enemies at school if they were threatened. 
- Decapitation - The most recurring type. Removes the head from the body through blunt force, forcefully removed or a slicing weapon (e.g., Baraka's 'Blade Chop').
- Immolation - Another common type. Victim suffers from severe burns from high-powered flames that often remove skin and flesh from the body, leaving behind charred bone (e.g., Scorpion's signature 'Toasty!').
- Bifurcation - Splits the victim in half at the waist area, vertically, or in the head (e.g., Kung Lao's 'Hat Slice').
- Explosion - Reduces the victim into a pile of gore through explosive techniques and/or devices (e.g., Stryker's 'Explosion System').
- Impalement - Runs the opponent through, often with a sharp weapon (e.g., Kenshi's 'Katana Attack').
- Amputation - Removes appendages through forceful means. Victim dies of blood loss (e.g., Johnny Cage's 'Torso Rip').
- Devour - Kills opponent by eating a part or their entire body (e.g., Mileena's Inhale 'n' Spit).
- Morphing - Changes into a creature to kill the opponent in a gruesome fashion (e.g., Shang Tsung's 'Kintaro Morph').
- Miscellaneous - Fatalities of a unique nature not shared with others (e.g., Deathstroke/The Joker's 'Gunshot').
- Animality - This finisher allows the player to morph into an animal and maul or eat their opponent alive. This style of Fatality debuted in Mortal Kombat 3. Some say the precursor to the Animality was Liu Kang's Dragon Fatality from Mortal Kombat II, in which he turned into a dragon and ate the upper half of his opponent. That Fatality was turned into Liu Kang's Animality in UMK3. Also, since Sheeva turned into a scorpion for her Animality, Scorpion got a penguin transformation. Due to this, the MK crew got complaints from the fans, so the crew added, in MK4, a scorpion transformation as one of his Fatalities.
- Brutality - Introduced in Mortal Kombat Trilogy and the SNES and Sega Genesis ports of Ultimate Mortal Kombat 3, this finisher allowed players to perform a combo which would end in a uppercut, causing the opponent to explode. Brutalities were not very popular, as they were extremely difficult to accomplish, requiring the player to memorize and perform a special 11-hit combo. Many felt the pay-off was lacking with the only result being a fiery explosion where the victim disappears and an unrealistic amount of bone and flesh are sent flying and covering most of the screen. In some versions, the bone and flesh flies completely offscreen. This finisher didn't appear in another game until Mortal Kombat: Shaolin Monks, in which it wasn't explicitly used as a finisher, but rather as a power-up.
- Weapon Fatality - In addition to Mortal Kombat: Tournament Edition one Fatality by character, there's also a new kind of (unlockable) finisher. The weapon Fatalities are basically Fatalities, but all the character does is to use his/her weapon of style to kill his/her opponent making a combo of the normal weapon moves. MK:TE is the only one to have it, since that the MK characters have Fatalities through their history that use his/her DA/TE/D/U/A weapon fighting style that are counted just as 'Fatality'; also, when one of those are performed, the announcer also says "FATALITY", in the same time that the game displays "WEAPON FATALITY".
- Multality - Mortal Kombat: Shaolin Monks also features Multalities, which are Fatalities performed on multiple enemies at one time. This was the only Mortal Kombat game to ever use this finisher.
- Heroic Brutality - In Mortal Kombat vs. DC Universe, many of the DC characters are superheroes who have sworn an oath against ever taking lives, Superman and Batman for example. Instead of performing Fatalities, they can perform Heroic Brutalities, which severely injure their opponent, but leave them alive to face justice. It should be noted, however, that villains from the DC Universe have no such oath, and perform Fatalities, not Heroic Brutalities.
- Babality - The defeated characters turns into a baby, sitting on the floor and wearing a miniature version of their adult clothing and accessories and/or a diaper (nappy) while crying. In some versions, the sound effect of a baby crying plays, along with a lullaby, and the word "Babality" is spelt out by colored building blocks that fall from the top of the screen. The announcer then declares (Albeit unusually and unnervingly gently) "Babality!!"
- Friendship - Instead of injuring the loser, the victor will make a peace offering, such as Sub-Zero using his powers to make a snowman, Scorpion startling his opponent with a skull in a Jack-in-the-Box, Liu Kang dancing while the disco ball appeared in the stage, or Johnny Cage offering a signed photo of himself. The announcer is generally disappointed when a match ends in Friendship, saying "Friendship. Friendship?" or "Friendship. Friendship? Again?"
- Fergality - A finisher performed by Raiden in MKII for the Mega Drive, the defeated characters turns into Probe Ltd. employee Fergus McGovern, who worked on that port of the game.