Being unrivaled or incomparable; unsurpassed. A literary/poetic expression used to praise someone or something as matchless.
彼の書いた小説は技巧と想像力で天下無比だと評された。
His novel was praised as unrivaled in craft and imagination.
あの剣士は天下無比の腕を持つと言われている。
That swordsman is said to possess unsurpassed skill.