Which enemies do you find most difficult to fight?

I don't like fighting against Death creatures (Vampires, Bone Dragons, etc.).

Added after 13 hours and 12 minutes
And I also don't like various ranged units (Poison, Beasts, Titans, Elves) with additional abilities (Poison - poison, double shot, no penalty at range).

Added after 2 minutes
P.S. Bupuppi, where did you get the character image from Heroes?