If you look at the picture you can see his description.------>
He has been called many names, like bloodthirsty, evil, and ambitious.
It is true that he killed his brother and wiped out most of his former clan, Shadowclan, but his brother tried to kill him first.
He is actually very caring, though he tries to hide it.
He is guided by Bluestar Tigerstar(who is his ansestor), because of a prophecy telling he would unite the Dark forest and Starclan.