Eddie Cieslewicz

, a.k.a Sledgehammer, was the unsub of 1x03, "Dexterity." 

Timeline: June 2007

Location: Chicago, IL

Age: unknown

Classification: Gamma

Gammanalysis
Crack: conflict between left-handedness and religious/abusive upbringing. "The left hand is the Devil's hand." 

Manifestation: super-strong left hand

Victims: 5 left-handed people killed. A sixth, his brother Dyson (Dice), was only crippled.

Current status: Held at Idlewood facility

Quote
''Dice was only half awake; he hadn't gotten to bed until nearly four, still reeking of cigarette smoke and beer and other people's sweat. "Eddie? Man, haven't you heard of knocking?"

''"I mean it, Dice." Eddie was already standing beside the bed. He was built like a bulldozer, but he could move fast when he wanted. "This left-handed crap has got to stop."

''Dice sat up, left hand groping automatically for his glasses. "What the f--"

''Eddie caught Dice's left hand, pinning the wrist with his own left hand, his right hand folded around Dice's fingers. "I'm sorry about this, I really am, but you just don't fucking learn."

''And with a single sharp motion, Eddie Cieslewicz broke all four fingers on his older brother's left hand.

--Eddie demonstrates his abilities, in the episode Dexterity