I think one place Coles anger comes from is his dad. The thought of how much his parents don't care really angers Cole. Cole gets very angry at his dad especially of how he beats Cole at home.
Another place Cole gets his anger is when he thinks about the Spirit bear and what he did to get hurt. I think Cole doesn't like thinking about the spirit bear because the thought about how he got kicked off the island comes to mind.
Another place Cole gets his anger is when his thoughts build in his mind especially at night. I believe Cole gets angry when he thinks about what he has done in the past like hurting Peter. Cole also gets very angry when he does all the work and no one else helps.