Peter Pan makes his first appearance as a boss in Kingdom Hearts Birth by Sleep. He is fought in Terra's storyline in Neverland due to Captain Hook's trickery. The devious pirate ensures that the battle takes place by tricking Terra into thinking that Peter Pan is stealing light from the treasure box.
For the most part, Peter Pan flies around the arena occasionally diving to stab Terra with his dagger (his only move). Simply dodge this weak attack and strike Peter when he's low enough to hit. The Sonic Shadow Shotlock is a good choice for this battle as it can do major damage. Just dodge his stabs and attack with proper timing until Peter is defeated; the battle will end before Terra is able to finish him).
Alternatively, if one starts attacking him from the beginning of the battle and manage to get the timing right to give him no break, he can be defeated without landing a hit on Terra.