Helping Hands, Iron Fist - S1-E4
Revealing mistake: When Iron Man appears on the screen in the Hulkbuster armor, if you look at the background behind him, there is a closed door behind him to his right and a control panel directly behind him, which means he appeared from out of nowhere.
Answer: The Hulk is a giant brute who smashes everything in his path when he is angry. In Ang Lee's "Hulk," General Ross, played by Sam Elliot, explains it to his daughter.