Well, Flash acquires his powers when he's exposed to a combination of a certain chemical mixture and a powerful bolt of lightning. This unique event triggers his super-speed abilities.
The way Flash acquires his powers in the comics is often a result of a chance encounter with a complex set of circumstances. Usually, it involves a laboratory incident where he's exposed to a mixture of chemicals and a burst of lightning, granting him his speed powers.
Deadpool got his powers through a messed-up experiment. His body was subjected to a procedure that gave him superhuman abilities, but also left him scarred and crazy.
The Hulk got his powers through a gamma radiation accident. Bruce Banner was exposed to a huge dose of gamma rays, and that's what transformed him into the Hulk when he gets angry.
Morbius gained his powers through a failed experiment aimed at curing his rare blood disease. The process transformed him into a vampire-like being with enhanced strength and other abilities.
Deadpool got his powers through a rogue experiment. A weapon program tried to give him enhanced abilities, but it went awry, resulting in his unique powers and messed-up appearance.
Kraven got his powers through a combination of genetic enhancements and intense training in the wild. He developed enhanced strength, speed, and senses.