I don't think he's evil but I do think he is easily swayed by power which is why he went to Orochimaru in the first place. It also makes him the perfect Indra transmigrant because Indra too thought power was the way to control things. Tobirama was right when he said that emotions did something to Uchiha brains that causes their eyes to change. I think the rinnegan, which Uchiha are not supposed to have, warp them or make them crazy in some way. He seems as crazy as Madara at the moment. He has always been, self absorbed and arrogant but threatening to kill the hokages is a bit much.
I expected him and Naruto to fight over the tailed beasts when he tried to burn them with ameratsu. You knew immediately at that point that Sasuke would never stand by and let them be free like Naruto wants. I assumed if given the chance he would try to kill the tailed beasts and Naruto would try to stop him and that would be how their battle would come about. I did not see the I'll become Hokage by killing all of the Hokage thing coming. That's just crazy. He learned absolutely nothing by how things went so badly for Madara, Obito and Kaguya trying to control everyone.
Naruto won't kill him because he wants to break the cycle of hatred and right the wrongs of the past, but he will beat him senseless enough to listen to the things that Itachi said to Naruto and to what lengths Itachi went to to try to save Sasuke. Naruto will tell him how Itachi planted Shisui's eye in a crow with a suggestion for Sasuke to protect the village. Naruto will also tell him to how Itachi told Naruto he should always let his friends and comrades help instead of doing everything on his own. He will also tell him about Itachi's thoughts on people who can become hokage, which he won't be willing to listen to until some of that arrogance is knocked out of him. He will be TNJ'd.