Which units in the Necropolis castle do you dislike the most (based on their appearance)?

No, the zombies are drawn really well, even the flies are buzzing around him, and their stats are consistent with their slow movement and attack speed. Zombies don't necessarily have to be peasants (then who would the skeletons be?).
But why do vampires need a sword, and why do they look like Japanese samurai? That's a flaw...