Originally Posted by
King of Asgard
That would only knock them down. The only way to kill WWZ zombies is by headshots. If you've read about the Battle of Yonkers, you'll know that despite having all the gear, the US military got its butt severely battered by the zombies. Explosives (like the ones on Stark and Rhodes' amours), were completely ineffective. This is because zombies do not feel fear. They do not panic like humans (or even Frost Giants) do. They are are not going to be awestruck when Thor does his fancy lightning stuff, or when Hulk says "Smash!!!". They are just going to keep on pushing. When Stark and Rhodes fire their missiles, all they are going to kill are the ones in the immediate blast radius. Many will lose their legs, and will become "crawlers". However, this will only make them more dangerous as they will be harder to shoot. Repulsors will only send them flying, they will not kill any zombies.
A major reason for the US military's defeat at Yonkers was that it assumed it was fighting a conventional army. All the evidence suggests that the Avengers would assume they were aswell. Thor would treat the zombies like Frost Giants or Chitauri: he would hit some with his hammer and ground pound the rest. None of this is lethal to a zombie. Hulk is the same, and as I have already stated, Iron Man's and War Machine's armours would not mortally wound many zombies, either. Of course, the Avengers are not going to be routed like the US military, but the OP states that they have to KILL every last zombie. If all they can do is contain the threat, then I'm afraid the undead win.