Board Thread:General Discussion/@comment-26006155-20190820122909/@comment-32182236-20190911173459

Betrayal attacks don't support Sans being a human. If it supports any strange claim, it supports the idea of Frisk being a monster (equally ludicrous)

We already know why Betrayal attacks work.

If a monster doesn't want to fight, its defense goes down. It also causes a human's attack to hurt them more.

So, if Frisk is affected by a betrayal attack, then either Frisk is a monster.. Or humans are affected the same way as monsters when it comes to their will to fight.

In the latter case, it should be possible for a monster to perform a betrayal kill, just as a human would, for the same reason why a human can do it. However, considering the overall lack of determination in monsters, they don't exactly.. think of that. By the time they think about sparing, they're already about to spare you for real.