A bomb's weakness should be fire. I imagine it would blast through ice, but fire should set it off prematurely. Thus, it would blow itself up, but nobody and nothing else.

Because, really, is it a "fire" enemy? No. It's a "bomb" enemy. It's explosive. Nuclear. They're two different animals.

Edit: Now I wish I'd voted for Lightning also. (I refuse to vote on Thunder as a synonym for Lightning. Thunder is a loud noise. That's it.)