A real meanie.
Someone who is a fail at life and does nothing to help himself.
A punk lacks common sense.
The accuser who is calling the other person a punk may be jealous of the other person's luck, life, or a mixture of both. Therefore the accusor must also be a punk.
Punk: Hey Chester! How's it goin? Look at this awesome mayonaise bottle I found lying on the ground!
Normal person: What a punk...