Leonardo DiCaprio, also as Alexander
It is ridiculously simple to deride Leonardo DiCaprio's work. The only one not nominated from the multiple award winning Titanic, he has always had to yell about his acting credentials, because he has unfailingly been the prettiest boy in Hollywood. His work in the last few years, however, has been rather impressive, and his acting resume has seen endorsements by directors like Martin Scorsese.
This part, however, is his because Luhrmann's film is clearly dealing with the more homosexual side of Alexander. And because he still looks that young.
Leo might have finally blossomed into a relatively credible performer, and worked for roles such as King Louis XIV in The Man In The Iron Mask, but he still lacks the power required to be dominating a film on his own merit.
Even for his admirable floppy-wristed capabilities, he played a ghastly version of French poet Arthur Rimbaud in Total Eclipse, turning it into a shallow performance of gay overacting and mediocrity.