Envy FTW! Seriously, this is one awesome character. You are supposed to hate him for causing the Ishval War, killing Maes Hughes and then framing Maria Ross for the murder, and to shape-shift into anyone to fool someone. However, he does have a witty side to him and can act with no reason to fight. Then when he gets mad, he sometimes can act like Ed.
In Brotherhood, Envy's character was even more brought out. When it was revealed to Mustang that Envy killed Maes, I halfway felt sweet justice that he got knocked back a few pegs, but at the same time his flame punishment was too harsh for words and you could sense the fear he had towards Roy.
The end of his life was really sad. Envy in his cute yet ugly slug form is so helpless and sad anyways. His suicide was justice served but also so painful to watch. I don't know, I guess seeing a small, crying thing draws out the pity in anyone.