Punishment is the act of attacking an opponent while they are vulnerable. Being vulnerable to be punished often results from using an attack with slow start-up lag at a non-opportune time or having missed an attack with high ending lag. For example, the Falcon Punch is a punishable move since it has long start-up and ending lag; if Captain Falcon uses it against an active and expecting opponent or if the move's target is able to avoid the attack, they have ample time to launch a counterattack. Characters can also be punished if their attack is shielded, such as via shield grabbing or out of shield attacks. An attack that is difficult to punish is usually known as "safe", usually due to having low ending lag and/or large hitboxes that are difficult to get around. A move's power can make punishment seem more dangerous; some players may choose to avoid the forward smashes of Ganondorf, Ike and King Dedede rather than attempt to punish them simply because of the risk involved. Actions that are less subtle are often punishable as well.
Some characters can use attacks with super armor for a unique kind of punish, although this is only prominent in Brawl and significantly more common in SSB4 and Ultimate. For example, Ike's Aether has super armor that allows him to tank and punish enemies who attack him before he throws his sword, while Little Mac's smash attacks in SSB4 and Ultimate all provide super armor, allowing him to punish any sort of laggy attack, weak or strong, by simply plowing through it.