I've noticed that when I activate Raiden's level 2 Super and try to kill an enemy by slicing with the right stick. they seem to get hit by the first slice then get ejected out of my attack, usually uninjured.
It was a small nerf when sackboy was nerfed. Usually if raiden killed with it it would give him extra AP(as if it wasnt cheap enough)
I think it was pretty fair, it had very short range and if you didn't finish them before the super ended they still wouldn't die. But this I'm pretty sure this is a bug, as it is nearly impossible to kill with it now.