>>712919912A garden can't instakill two classes if they're at full HP, and 5 if they're overhealed (assuming no weapon vulnerability or HP changes).
I think, however, that a fists of steel heavy will always die in one hit, even at max overheal, which is very cool. That is, unless they've eaten a Dalokhs Bar, but I don't think I've ever found myself in that situation. I haven't done the math so maybe I'm wrong.
And caber is a one-time explosion, so it's sadly hardly useful