Refers to the act of taking revenge, especially in a historical or dramatic context. Often associated with samurai tales of avenging a master or family member. In modern usage, it can be used metaphorically or in literary contexts.
復讐 is a more general and common term for revenge, while 仇討ち carries a stronger historical or dramatic nuance, often implying a duty-bound act of vengeance.
敵討ち is a synonym with a very similar meaning, but 仇討ち may emphasize the personal grudge (仇) more than the enemy (敵).
Etymology
Compound of 仇 (ada, 'enemy; grudge') and 討ち (uchi, 'attack; strike'), the nominalized form of 討つ (utsu). The term is historically associated with the samurai practice of avenging a slain lord or relative.