Tony is a tough cookie in one of his suits and can go toe-to-toe with the others. But when an obscene number of iron men are perfected by Ultron and operate without human error, they roll over and die by the hundred. If you pay attention you can see the bots act like retards and assemble themselves to be wiped out without making any effort to fight back. The fight should have been the most one-sided mercy killing imaginable; Ultron was far too powerful an opponent for these non-comic-godmode superheros.