The whole discussion they're having about how Slad is unaware of his skill and won't depend on it, or actively use it or anything else of the sort is nonsensical because we have already confirmed through his rescuing of the heroine that he is fully aware of the consequences of his skills, how it functions and how long it takes until people literally die from the debuff if they continue opposing him.
He has actual knowledge that given enough time for his debuff to stack, that he is always victorious. So he is simultaneously extremely aware of his skill for the purpose of combat and resolving threatening situations. But also equally unaware of it for the purpose of him having no self awareness for the purpose of creating drama and misunderstanding.
That is a lot of buuullllllsheeeet.
So I take it that he's going to go help them out one at a time with the guy being last and discovering him having his fantasy of raping the women and his debuff will activate automatically and slowly kill the guy.
Also what're the odds that the Demon King is already being impacted by his debuff skill and may actually be long dead before they even reach the Demon King since we have no clear idea of the range limitation of his auto debuff/buff.