I dont know if y'all know this, but theres a parry system in-game. When you block the first m1 of your opponent, your first m1 deals a highest damage to him.
for fact 2, add 2 dummies, put on finishers only,,Use flowing water on the first dummy, then at the last hit of flowing water, hit the 2nd dummy, its a thing i know, if it doesn't work, *do it again*
the secret finisher happens when you kill someone low (like a finisher) but not the target you hitting. I mean, flowing water haves hitbox that can hit nearly players, so the near low player gets hit by the last hit of flowing and gets flinged like the finisher
I think to get a similar effect to garou's 2nd finisher you could hit a low hp players with flowing water's attack itself rather then "grabbing" them into the animation (Poorly worded but i hope u understand)
if you want to do garous old finisher you need 2 dummys/players low hp hit one with flowing water and the other with the attacks of it then they get sent flying :)