Killer Instinct plays like many other fighting games, in which the player controls a character to beat an opponent in a one-on-one encounter. The game borrows the attack set of Street Fighter and is also inspired by the finishing moves from Mortal Kombat. There are also several features that distinguish it from other franchises:
A double health bar: Each player begins a bout with two bars of health. Victories are decided not by the best-two-out-of-three format common to other fighting games, but rather by the first player to exhaust both of their opponent's bars. In addition, players do not recover any health after draining the bar once.
Automatic combos: Many combos are automated, after an initial button press sequence.
Finishing moves: Bearing resemblance to (but being less graphic than) Mortal Kombat's Fatalities, each character has at least two moves known as No Mercy (Danger Move in later revisions) to finish the opponent. Another finisher is the Humiliation, that forces the opponent to dance.
Ultra Combo: Another finisher, it operates like an Ultimate Combo, though this one allows the character to deliver a long string of hits as the combo finisher instead, usually surpassing 20 hits, and can sometimes reach upwards of 80 hits.
Combo Breaker: The player who is being caught in a combo may escape it by performing a breaker move. A combo can be broken at either the auto-double or linker stage. After a character performs a combo breaker, the leading edge of their health bar will flash white, enabling advanced versions of some special moves that require a different command.