“I thought Iron Man and Hulk is the same side, why are they fighting?” is the common question we got asked a lot.
In Avengers: Age Of Ultron, Scarlet Witch is the person who brainwash Bruce Banner, makes him destroy the city unwillingly. In order to stop the strongest Avenger, Tony Stark cannot use his normal suit. He uses the new power tool called the Hulkbuster, with a flying mechanic to replace damage parts immediately.
But the powerful Hulk is too strong, even with the carefully preparation from Tony. Hulk deals heavily damage to the city, as well as to the Hulkbuster. In order to protect the citizen, Iron Man must bring him to somewhere quiet while dealing with his angry side. The Hulkbuster lost an arm, the back armor, boost rockets, along with the whole flying spare parts system.
In the end, Tony Stark must drop the Hulk from the sky to an constructing building with no person there. Heavy injured, Bruce Banner can somehow escape from the witch’s spell, realizing what he has done to the citizen, before having a knockout punch from the Hulkbuster.