Little is known about Levi's past other than he has some past history with Cal, has a genius level IQ, and has no regard for the lives of others. He also expresses a generic dislike of food.
Fight On Edit
In "One of Us", Cal found Levi living in an RV in the middle of Mojave Desert. Cal removed the chip in Levi's arm and offered him the opportunity to get revenge on S.H.I.E.L.D. and show the world what S.H.I.E.L.D. does to gifted individuals like them. Levi hacked into the Index for Cal so he could get a list of other Index members.
Levi next helped Cal break into Brynmore Psychiatric Hospital by disabling the hospitals security systems.
Cal then leads his team to Mantiowoc, Wisconsin, Coulson's home town, ensuring Levi and the others that S.H.I.E.L.D. would come to them. After Levi and the others attack a local high school, Coulson and his team do appear. However, right in the middle of a stand-off, Gordon teleports in and grabs Cal before teleporting out.
Levi is knocked out by Coulson as he tries to flee the scene and then presumably arrested.