Most of his no longer work.
I know you can use "Ground down +circle (banana)"
But that takes too long and gets interrupted.
air Down triangle doesn't work that often on moble characters..... so are there any practical ones left?
They all work. Spike's a character more about fishing for his various kill confirms throughout the match. If he can't get any, then he uses his incredibly easy kill confirms for his level 2.
Fresh to death
Just to follow up I have the most luck with the down triangle confirm, though as I have been working on his RC car loop I have been landing that confirm a bit more as well.
It's unbelievable when compared to Sackboy's FP's Raiden's EC and Toro's (ones that I've tried.)
I always use air down triangle. I don't use it just for hit confirms. I use it as my basic attack until someone gets hit by it then I follow up with one of his square combos. People don't expect it as a hit confirm when I'm using it the entire match.