And we have no idea what the capabilities of any of them are unless there is someone from their world. Which is why we need a complete list. Even then, there are so many different situations.
[A pause, before adding.]
Just brainstorm a few situations from two people from the "hunter" side.
A de-aging malfunction sending Headmaster back to the period of time in his life where he indiscriminately slaughtered vampires.
Something removing the moral compass from myself in a similar manner to what happened to you.