[@Old Amsterdam]
Unbreakable skin just means the skin has to go wholesale. Humans expire when they lose around 70% of their skin, so just removing someone's invincible skin wholesale is still pretty damn lethal. Assuming it's actually 'unbreakable' and not incredibly damage-resistant, which would not prevent Guilt's transportation abilities.

And regeneration is a good way of surviving otherwise lethal abilities, but Void allows her to store beings like that indefinitely until they can be disposed of. Dropped in an active volcano, for example, or buried in cement. Even if they survive, they won't be doing much.