It depends whose animating the Destroyer. But because Mangog only managed to lift the Odinsword, which requires multi-planetary level strength, I'd say that the Armor would no sell his punches.
You may have missed that Desak is in the Destroyer. I'd place my money on Desak killing Mangog without the armor, with it I'd also give him the win, but I think that it would be quite a battle.