There are two ways to avoid the underground room bad end-
>The first is getting the right answer
>The second is getting all the right answers to particular previous choices which will give you a free pass to whichever answer you give to the underground choice
So yeah! Think of it as 'all your choices matter' cause they can make later choices more difficult or easier. There isn't just one way to avoid the bad end. The same goes for the other bad end.
But you're on the right track- they are villains after all, so you have to have the mindset of how to deal with them!