certain victory; invincibility
Emphatic compound meaning absolute victory or being unbeatable; often used in motivational or martial contexts.
He approached the match with an unwavering belief in certain victory.
This strategy was devised with the aim of ensuring invincibility.
必勝 means 'certain victory' and is more common; 必勝不敗 adds 不敗 (undefeated) for stronger emphasis.
不敗 means 'undefeated' or 'invincible'; 必勝不敗 combines both concepts into a single emphatic term.
A four-character compound (yojijukugo) combining 必勝 (certain victory) and 不敗 (undefeated). The exact origin is uncertain, but it follows a common pattern of pairing near-synonyms for emphasis.