I say Kakashi for these reasons:
His father commit suicide.
His best friend was crushed in front of him, to save him.
He had to kill his other friend.
His sensei was killed.
He lost one of his students to hatred/revenge.
He found out about 20 years later that his best friend actually was not killed, but, was killing others for a selfish dream world.
And, he still does things for good reasons, tries to help others etc.
Naruto comes second.
People like Sasuke, Obito, Madara all let their feelings get the better of them and started going on a selfish killing spree.