Trauma, something that someone experiences that is life changing that makes the person do something about it.
Destiny, pretty much this certain person was meant to be the chosen one.
Luck, the chance that this person gain some power from something random and goes around the world saving people.

Mike is this kid that doesn't really have friends do to the fact that he is the bully of the school pretty much. No one has ever liked him and soon enough kids got together and told him to stop. He had to back down since they were just teaming up on him. He was more angry than he has ever been. On the way home he ran into a old man telling that his fate is going to be dark and evil if he doesn't change his ways. This continued on for 2-3 years and when things could have been better, they got worse. His hatred grew so strong that he turn into hatred itself, a manifestation of hatred. He was dark and evil just like the old man had said to him a few years back. He was able to shoot shadow though his hands furiously and be able to turn into shadow itself where he cannot be touched. From this day on he was called Shadowria.