then it will teleport them to the backstab. If you use debug to take control of your co-op partners character, it has no effect on them UNLESS you backstab an opponent. You can do this to just about any character in the game. You can enable ragdoll on your co-op partners for hilarious results (it's only visible on your end - no effect to the companion) The current dream of 'boss vs boss' PVP isn't possible unfortunately. The only way for someone to maliciously attack someone with a boss currently is to teleport a boss in, make them invincible, and set their team ID.
If someone is playing as a boss with the debug, the other person in game doesn't actually see them and doesn't take damage from their attacks. The debug version can connect with the Steam Beta version as well as other debug versions. I just spent like 7 hours working through a bunch of debug stuff with someone and learned so much.