His voice he uses sound rather similar to an infamous portrayal of another evil emperor whose name also starts with C. Phoenix quite clearly seems to be imitating that actor with his performance. After all they both play evil emperors who murder their predecessors, and they both wish rather for a relationship with their sister which is far too close. Phoenix really imitates this earlier performance, and really I should not even say imitates but rather really rips off the earlier performance. He has the same evil voice, self-indulgent manner of movements.
Phoenix I suppose is creepy but any actor could be creepy quite easily since the character himself is simply just that. He really does nothing more with his character than one would expect. He makes Commodus a fairly one dimensional evil villain. Instead of trying to suggest more depth of Commodus he just does the evil emperor routine which is expected and includes a lot of flamboyant overacting that was not very impressive. Now a villain can be one dimensional, and an actor can still excel by making their performance incredibly entertaining and effective. Phoenix does neither making his Commodus a rather unoriginal simple, a not very entertaining villain.
