out of one's league; facing a too tough opponent; outclassed
Colloquial expression used when one's opponent or rival is clearly superior, making the situation disadvantageous. Often used in sports, games, or competitive contexts.
The next match is against a tough opponent, so it'll be hard to win.
彼と議論しても相手が悪いよ。彼は弁護士だからね。
You're out of your league arguing with him; he's a lawyer, after all.
A fixed phrase composed of 相手 (opponent) + が (subject marker) + 悪い (bad). The literal meaning 'the opponent is bad' developed into the idiomatic sense of being outmatched.