In the Avengers: Age of Ultron, the Scarlet Witch and her brother team up with Ultron against the Avengers for a while. In a few scenes, she uses her mind-powers against them.
She shows Tony Stark (Iron Man) what happens if he fails, with the pile of dead bodies of his friends, and Steve says "You could have prevented this" (or something like that).
She shows Steve Rogers (Captain America) the life he never got to live, with the dancing and the woman he loved.
She made Natasha (Black Widow) relive her painful past, where she remembered her childhood having to dance, and the sterilizing in the secret room.
She had Thor foresee an impending doom, that in the end had him haring off to find his friend and get the information about the Infinity Stones.
But she also showed Bruce Banner (Hulk) something that made him 'turn green' and become Hulk and go on the rampage. Seeing as he had by that time controlled himself a little better, it must have been something really bad that made him change. What did the Scarlet Witch show him?