While Igor Karkaroff isn't the most evil character in the Harry Potter universe, he's certainly the most contemptible. He follows Voldemort and commits horrible atrocities in his name, only to turn traitor and name names as soon as it seems like it's in his best interest. Despite all the terrible things he's done, he manages to carve out a respectable life for himself as the headmaster of Durmstrangs. But then when Voldemort comes back and it's time to pay the piper, he takes the coward's way out and runs away. Say what you will about the diehard Death Eaters, at least they had principles. At any rate, exactly zero tears were shed when it became known that Karkaroff was hunted down and killed.