Jack Ryder was just a reporter in Gotham City until he takes a serum from a doctor that turns him into a powerful hero...and also insane.
When he is under "control", he has superhuman strength and agility, is a proficient acrobat and martial artist, and has a healing factor that makes him nearly indestructable. He also has a laugh that can actually harm his foes when it goes loud enough.
As a resident of Gotham City, Ryder seeks to "protect" the people when he can, but the insanity of The Creeper can sometimes make that a painful process. Regardless, Batman and his allies have made a partner of Creeper, and he's helped them on numerous occasions.