decisive blow; finishing move
General term for a decisive action that settles a contest, argument, or situation. Used in sports, combat, and figurative contexts.
His single remark became the decisive blow in the argument.
The boxer landed the decisive blow in the final round.
game-winning hit; clutch hit
Specifically in baseball, a hit that drives in the winning run or breaks a tie late in the game.
In the bottom of the ninth, his timely hit became the game-winner and the team won.
決定打 emphasizes a forceful, punch-like blow or piece of evidence that seals the outcome, while 決め手 can be any key factor, however subtle.
決定打 means a decisive, game-ending blow or move, used figuratively like 特効薬 for a solution that settles a problem once and for all.
Compound of 決定 (decision, decisive) and 打 (hit, strike). The term likely originated in sports or martial contexts and extended to general decisive actions.