I like Hamlet's assessment of Claudius:
Smile and smile and be a villain!
Claudius is the consummate politician. In his ceremonial speech announcing his marriage to Gertrude, he soothes over what might have been a sticky public relations problem: a marriage to his dead brother's wife. But by explaining that the marriage was necessary for the state and by rapidly taking care of other business at hand, Claudius assumes the role of king with apparent ease. Yet, it must be remembered that his killing his brother is what begins the conflict in Hamlet. This act results in the destruction of many lives around him and has consequences beyond what he thought possible. So while he is happy and content in his new role as king, other lives have been and will be shattered.