noun
grudge match
A match or contest held to settle a long-standing grudge or bad blood between opponents. Often used in sports, martial arts, or dramatic contexts.
両チームの遺恨試合は、激しい展開になった。
The grudge match between the two teams turned into an intense battle.
あの遺恨試合以来、二人は一度も言葉を交わしていない。
Since that grudge match, the two haven't exchanged a single word.
Similar in meaning but broader; can refer to any fateful showdown, not necessarily a formal match.
Compound of 遺恨 (いこん, 'grudge') and 試合 (しあい, 'match'). The exact historical derivation is uncertain, but the term is conventionally associated with settling old scores through competition.