I was wearing my Cthulhu shirt today and my 3yo son asked who it was. He's big into the (Lego) Marvel Pantheon at the moment, so I explained he was a super duper villain. My son immediately suggested Hulk might punch him.

I don't know if Hulk ever did a Cthulhu crossover. Batman surely did, but I feel like Marvel doesn't like anything unexplainable.

@brettwitty Marvel has featured Lovecraftian entities many times, usually in stories involving Dr. Strange. Hulk was a member of the Defenders with Doc, and in the storyline in Defenders v1 n72-83, they fought the Unnameable. I think old Jade Jaws did punch a projection of the Unnameable at one point, so I think that's close enough.