Combo Breakers are a special move in which a character interrupts a combo being performed on then by their opponent.
Concept & Execution
In the original Killer Instinct and Killer Instinct 2/Gold, Combo Breakers were not quite as essential and more of a side tactic. When caught in a combo, the defender can interrupt the sequence by performing one of their special moves, differing between each character. When done correctly, the defender breaks out of the combo, deals a large amount of damage, and resets all potential damage. Combo Breakers cannot be performed after a certain amount of hits have been performed by the attacker, so the move must be done quickly upon being caught in a combo. Combo Breakers also do not work on ender moves.
In Killer Instinct (2013), Combo Breakers became a much more vital part of battle. Combo Breakers can be executed by observing the strength of attacks in the combo and pressing both the punch and kick out of the corresponding strength - for example, if a player wants to Combo Break out of a heavy double, they would press both heavy punch and heavy kick to break out of it. The strength of an attack can be examined by how the other character reacts upon being hit. Upon a successful Combo Breaker, the breaker will gain some Instinct Meter and reset all potential damage racked up by the combo (note that it no longer deals damage to the attacker). In the case of Shadow Moves, a player presses a punch and a kick of any strength three times at the frame of each subsequent hit to successfully break - this results in what is called a Shadow Breaker. In addition, a penalty called Lock-Out is issued to a player that misses a Combo Breaker. This is signified by an X on top of the opponent's head with either the strength of the correct button or a clock signifying incorrect timing of the breaker attmept. Upon getting Locked-Out, the player cannot Combo Break for three seconds (four seconds if Counter Broken) or until the combo ends.
In Killer Instinct (2013)'s Season 2, aerial Combo Breakers were introduced, giving more depth to aerial combat. They are performed just like the ground versions. Later, in Season 3, Combo Breakers were adjusted so the attacker would no longer be knocked down, but instead flipped backwards so that they could move back into the battle much faster.
A Counter Breaker is another new move introduced in Killer Instinct (2013). It is described as "breaking the breaker," where the attacker can defend themselves from a Combo Breaker and continue their combo uninterrupted. The player baits the breaker in the middle of the combo with a feint, signified by a low tone. If the Combo Breaker lands while the attacker feints, they'll instantly Lock-Out the defender for 4 seconds (in comparison to 3 seconds for usual Lock-Outs) and the attacker may keep attacking, refreshing the knockdown value gauge to make for an even longer combo. If the bait isn't taken for the Breaker, the combo ends and the attacker is left open for the punish.
An Ultra Breaker was introduced in Killer instinct 2/Gold, In order to break them, you must have at least one full level on the Super Meter. You can only break an Ultra during the first 4 hits, before it begins to cycle into the Ultra's repeated hits. The Ultra Breaker does around 40% damage to your opponent and gives you a last chance to win!