I own a Sylvania 6620LDF 20 in. EDTV-Ready LCD TV/DVD and my cousin punched the screen and a big amount of color lines are popping out no image comes out, crak is still there, tv can still turn on but no image pops out

Return the favor to your cousin! Your TV is now dumpster material. The LCD panel (your cousin's punching bag) would be hard to get and far too expensive to replace. Have you cousin purchase you a new TV and then send them to anger management classes.

Regards

When he hit the screen, he most likely broke through the protective glass screen and broke the lcd screen that displays your picture. It's probably better for you to just replace the tv itself, it'll be more costly to repair the tv than to replace it.