Hunter Zolomon's turn from troubled youth, to friend and colleague of Wally West, to Zoom is both tragic and inevitable. With his pride getting his way, and the desk he sat behind, it only took a very violent, very breaking, push from Gorilla Grodd to help him become Zoom.
Paralyzed from the waste down, an accident with (ahem) the cosmic treadmill gave Hunter the ability to defy his physical limits and make up his own. He celebrated his newfound powers by extracting revenge on Wally West for refusing to help him when he needed Wally most. Rather, he took his anger out on Wally's wife and tried to murder her.
Wally West saved Linda's life, but Zoom's attack caused Linda to miscarry. This event forever paved the way of what our heroes could expect from Zoom, as did his ability to wield Personal Time Manipulation, which is just a fancy way of saying do evil things, faster than the Flash can maybe move to stop them. His speed is fueled by an ability to bend time itself, something only the fastest of Scarlet Speedsters can do is hope that they can keep up.