Leon Shappe was ruthless killer even before he got his super-powers as Speedfreak. At some point in his life, Speedfreek became addicted to the drug called "snap". He killed the owner and presumable inventor of his battlesuit in order to steal it. Once Speedfreek's daughter, Kate, discovered what her father was doing for a living, she ran away from home. Later, he was hired by a man called only Mr. Lang and had to kill his rival Ralph Badone. Speedfreek succeeded in that job, additionally killing the man's guards. Lang later also hired Speedfreek to kill the man who had infected his son, Tyler, with AIDS.
Speedfreek did as told and located Tyler and his partner at a musical performance during an AIDS benefit party. During the battle he injured both Rick Jones and Jim Wilson. Bruce Banner, aka the Hulk was also present. The Hulk ended the battling by literally throwing Speedfreek a very long distance.
Speedfreek's daughter was killed in front of an abortion clinic by a young, confused boy named Larry. Speedfreak attempted to kill Larry again and again, only to be stopped by the Hulk each time. The Hulk, after healing from many brutal cuts, ended this battle by launching a car battery at Speedfreek's face. He easily sliced it in two, but the acid in the battery hit his face, causing tremendous pain. He was presumably arrested soon after.
Speedfreek was also one of the villains that escaped from The Raft prison. Hiding in Stamford with some other escaped convicts, he was eventually tracked down by the New Warriors, who battled with him and his friends as part of a reality show. Nitro used his powers to destroy the entire neighborhood, causing both the death of hundreds of people, the New Warriors, and presumably Speedfreek as well.
Speedfreek wears a battlesuit that allows him to hover above the ground and fly at extreme speed using the boot jets. Weapons include arm-mounted adamantium cutting blades and adamantium projectile barbs. The suit can also generate a holographic image.