First of all things would not be different if it were Carnage. Why do people not understand that Carnage is weaker than Venom? He has consistently been kicked around by Venom and is not nearly as experienced. As for this battle, it's a bit odd, because Venom has the capability of taking down characters way out of his league. While Colossus can overpower Venom with relative ease, yes, Venom can suffocate Colossus with relative ease. It really depends on the writing.