A kill confirm, also known as a KO setup, is used to refer to a fast and safe attack that can reliably lead into a KO at high percentages. Kill confirms are considered a type of combo, but are different in that kill confirms are used primarily to finish off opponents' stocks, while combos are used to rack up damage. In addition, most true combos only work at low to mid percents, while kill confirms can connect at high percents.
There are several different types of kill confirms in the Super Smash Bros. series:
Kill confirms generally work differently based on the opponent's character; they will work at different percentages against each character, depending on their weight, falling speed, and acceleration. They can be significantly harder to connect, or not work at all, on certain characters, and as such, many kill confirms work only on one or a few characters. Their exact timings and percentages can be altered by rage in Smash 4 and Ultimate.
Kill confirms are considered one of the most reliable ways of finishing off opponents in advanced play. Most high-knockback attacks in the Super Smash Bros. games, such as smash attacks, are risky to throw out on their own, since they usually have high startup lag or ending lag, or a small sweetspot that is difficult to land, making them easily punishable if missed. A fast kill confirm circumvents these problems by being much harder to predict and react to. Grab-based kill confirms are especially powerful, because many players will opt to stay in shield more when at high percents, to protect themselves from getting killed by smash attacks and other strong moves; grabbing will ignore an opponent's shield completely and is a natural counter to this playstyle. A character with a reliable kill confirm can see their KOing ability improve significantly, even if the knockback of their finishers is weaker overall, and vice versa. In Melee, Captain Falcon is known for having one of the strongest KOing abilities in the game, as he has multiple different combo starters that can all lead to a kill off the side with his Knee Smash. Conversely, Marth is known for having a particularly difficult time KOing his opponents at high percentages without edgeguarding or gimping, as he has no reliable kill confirms, since his throws and aerials all do not link into each other well. As a result, is not uncommon to see opponents, especially floaty characters, survive to 200% and beyond vs. Marth.
However, some kill confirms are not always guaranteed, depending on the combo DI or smash DI of the opponent. In addition, some popular kill confirms, such as tech chases, require the player to read the action of their opponent, giving them an opportunity to escape. Although some kill confirms are difficult to react to, skilled players will often start their DI inputs before they get hit, which will allow them to escape the combo.
List of kill confirms
In Super Smash Bros. 64
In the original Super Smash Bros., most characters have several different kill confirms, which can often connect at extremely low percents, due to the game's large amounts of hitstun. Kill confirms are generally less prominent in Smash 64, as a result of the game's more significant punish game, which means characters do not live at high percents in neutral very frequently.
In Super Smash Bros. Melee
In Super Smash Bros. Brawl
Overall, Brawl has the fewest amount of kill confirms, due to the game's significantly decreased levels of hitstun.
In Super Smash Bros. 4
In Super Smash Bros. Ultimate