Erthenia

Can he be ignored with high willpower?

Nope.

Added 31 minutes later
I've just come up with a build that's a hundred times more overpowered than any of the ones mentioned earlier.
The idea: take an aristocrat, give him aristocrat followers, and keep doing that until you get bored, while also giving some of them normal abilities. In the end, you'll have a huge amount of money and a personal army.
But you shouldn't do that.

Stats for summoned skeletons:
Melee damage modifier: 0
Health: 50
Melee accuracy: 20
Ranged accuracy: 20
Melee evasion: 20
Ranged evasion: 20
Magic evasion: 20
Movement speed: 10
Initiative: 1
Magic resistance: 0
Action points: 0
Basic proficiency with all weapon types.

Immunity:
Flame of Passion.
Water Prison.
Suffocation.
Shock.
Creation Magic.
Zetsumэй.
Confusing Mist.
Plague.
Oblivion.
Mind Transfer.
Cloud of Death.
Desiccation.
Dreams.
Otherworldly Gaze.
Channel Disruption.
Subjugation.
___
Bleeding.
Harvest.

Cold Aura
Poisons
___
Ranged weapon damage reduced by 90%

Combined skeletons receive the following bonuses for each new batch of bones:
+75 health
+0.2 melee damage modifier
+5 evasion and accuracy