After seeing his family hang, he wanted to enact revenge on the Borgias. But, over the course of ACII he became a seasoned Assassin who showed strength in not taking the life of the head Templar, the one who ordered his family's death. He uses this strength to lead the Brotherhood in Rome too in AC:B. And he also refuses to take the Apple at the end of AC:R saying that he didn't understand the power it possesed and let it be. Unlike Altair, Ezio also never broke ALL tenents of the creed in the course of 5 minutes.