That's the thing about Tonpa, he loves messing with other applicants to make em fail on purpose but he doesn't exactly have a death wish about it. If he sees that the applicants he's sabotaging are truly powerful and cold blooded enough to kill out of anger, or fun, then he keeps a healthy distance from them; like Hisoka or Hanzo. In other words, Tonpa's a big old cowardly bully who picks on those who can't fight back. The fact that he's messing with our guys here means that he's certain he can escape any violent retribution. Or overestimates his ability to handle them, idk π.