Do I tell my coworker that he smells bad?

TLDR: my coworker smells really bad and I don’t know if I should tell him.

I sit diagonal from my coworker in the office. He’s a nice guy. Issue is he stinks. On a scale of 1-10 with 10 being unbearable, it’s a 9. He has really strong BO; it lingers in conference rooms after he leaves. Every time he moves, you can smell the BO.

I want to tell him politely that he smells so he can be more mindful, but I’d be mortified if someone did that to me. I don’t want to hurt the guy at all. If I don’t say anything, I don’t know if the situation will change.

Do I say something or should I not?