Whats it doing? Is it a black screen, white screen, flash failure message, what? Did you try a different battery? If you can get it to fire up you can rsd it back to stock ics.
sent from my icy bionic
What did you do to screw it up? There could be a dozen or so reasons you're having problems, but if you don't go step by step to tell us what you did, all we can do is speculate.
The Aphotic Chaotic
LG G2 VS980 (Verizon) [JB 4.3] PAC-man ROM
Nexus 7 [JB 4.2.2] XenonHD