Part of the problem is that he only becomes Unstoppable when you dash back, so you'll have a very tiny window to then punch him and remove it.Secondly, if you succeed in doing that, Annihilus's Cosmic Control Rod protects him from Nullify. You'll fail to Nullify the Unstoppable; and instead either (a) fail to remove the Cosmic Control Rod because CAIW can only Nullify Unstoppable or (b) succeed in removing the Cosmic Control Rod; and trigger "Its Miine!" giving him a massive Fury Boost (whilst he's still Unstoppable).As another option, She-Hulk or Spidergwen should work against his Unstoppable. But if you've got him at a competitive rank, Kingpin is the absolute best counter there is for Annihilus.