#1: Neymar and Edinson Cavani

This incident occurred in PSG's recent weekend match in Ligue 1. PSG grabbed another victory by defeating Lyon 2-0. But, the tension between the players seemed to persist even after they had left the field.
PSG received a penalty and Edinson Cavani decided to go for it. Neymar came forward and asked Cavani to let him take the freekick. The Uruguayan's behaviour deeply angered PSG's record signing Neymar. Previously, Dani Alves had already denied Cavani a free kick by handing the ball to Neymar.
The disagreement ended in a changing room bust-up and the players had to pull them apart from having a go at each other. This is a fine example of how selfishness upsets the changing room harmony.
Further, reports state that Neymar has already asked the officials to get Cavani transferred in the next season. The Brazilian's ego and intention of becoming PSG's main man might cost them a celebrated striker like Edinson Cavani.