頭が悪い

stupid

→ 頭
phrase Rare #41,178
stupid Literally “having a bad head,” this is a blunt and often insulting way to say someone is unintelligent or foolish. It can also mean “not very smart” depending on context.
JA: そんなに頭が悪いわけじゃないよ。
EN: You’re not that stupid.

頭が悪い

You're stupid, you know.

ここだけの話だが、彼だいぶ頭が悪いと思うよ

Between you and me, I think he's pretty stupid.

ただ単に頭が悪いだけじゃねえのか

Could it just be that you're stupid?

— AKIRA (1988)

頭が悪いばかり生意気それに恥知らず

Not only are you stupid, but you're also insolent—and shameless to boot.

— 大人は判ってくれない (1959)