It is almost an official duty of an Action Hero to deliver sardonic one-liners. And what better time to produce one than just before the execution of their other official duty — kicking ass.
Common variations on this trope include:
A form of comic subversion in which the one-liner is stupid or silly. This has the potential to stall or confuse the opponent.
A form of comic subversion in which the outcome of the intended ass-kicking fizzles, negating the one-liner or at least failing to justify it.
A Catchphrase or Battle Cry that may have started as a one-liner, or may work as one to some degree.
Carrying an Improvised Weapon and matching the response accordingly (for example, Anchors Away or Batter Up!).
The hero does not clearly say his one-liner at first. The villain tells the hero to speak up, leading into a properly-delivered example.
The Hero and The Rival, the Big Bad, or another suitably-meaningful nemesis exchange one-liners immediately before throwing down. This may or may not be followed up by Casual Danger Dialogue during the fight itself.
Chew Bubblegum and The "Why Wait?" Combatant are particularly popular examples. See also Badass Boast, Badass Creed, In the Name of the Moon, and My Name Is Inigo Montoya. Contrast Pre-Mortem One-Liner, which is often used to end a fight (namely before killing someone), or Bond One-Liner, which is used once the fight is over.
