A Fatality, introduced in the original Mortal Kombat game and having since appeared in every game in the series, is a Finisher performed by the victorious player's character at the end of a match during the Finish him/her! period using a specific sequence of inputs within a limited time after winning the match.
Staying true to its namesake, a Fatality is a character brutally killing off the defeated opponent at the end of the match. Fatalities throughout the series all require many different fundamentals for them to properly function. Characters must properly be set in the correct distance from themselves and the opponent before performing a Fatality. Once the correct input is entered in, an animation would play, showing the victorious player performing the finisher, to which the announcer promptly exclaims after the execution, "(Character's name) wins! Fatality!"
While creating Mortal Kombat, Ed Boon and John Tobias, the co-founders of the Mortal Kombat series, 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."
In Mortal Kombat: Legacy Season I, Baraka uses his Blade Lift Fatality on one of King Jerrod's decoys, and Cyrax performs a Fatality on Hydro, decapitating him with a forked blade from his wrist. Later in Season II, several Fatalities are performed by the various kombatants of the tournament: Kenshi telekinetically thrusts his sword, Sento, through Ermac's heart, Kitana decapitating Mileena with her fans, and Scorpion performs the classic Spine Rip Fatality on Sub-Zero.
- 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.
- The first Mortal Kombat game is the only one not to have a "Fatality" graphic like the ones that appear onscreen when the move is performed in later games.
- In MK 2011, each character exclaims a battle cry before performing a Fatality, e.g. Scorpion crouches and fiercely shouts, and Johnny Cage says "Watch this!".
- There are ten characters in the series who have never received unique Fatalities: Blaze, Chameleon, Daegon, Darkseid, Khameleon, Meat, Mokap, Moloch, Onaga and Taven.
- In the game Trials 2: Second Edition, if you bail out from the bike or crash and manage to kill the rider, a voice will say "Fatality!"
- In a Top 10 list hosted by Screwattack.com, the Fatalities as a whole appeared as #8 of their Top 10 OMG WTF?! list.