Secret Wars II #5

Direct

The Beyonder dismantles a train that is about to hit him and one of the passengers turns out to be a young mutant traveling to Xavier's School. The Beyonder agrees to take her the rest of the way but, once they arrive, the X-Men ignore her in favor of attacking him. In despair at the rejection, Boom-Boom tries to kill herself with one of her time bombs but the Beyonder brings her back. He takes her on a cosmic jaunt to meet the Celestials and she freaks out when he beats them up. On returning to Earth, she calls the Avengers in for help and the Beyonder is crestfallen by the betrayal.