If we look at it, Toriko has plenty of weapons to off nappa in one shot. He has the 50 ren kugi icepick, 50 ren kugi punch, cannon fork+leg boomerang combo, and if that wont cut it, he could just use the 100 ren twin kugi punch to demolish him.
He can kill Nappa. There's no question there. The problem is that Nappa can do it too and Toriko has no way of avoiding his scale of attacks. Nappa's destructive capacity overshadows his durability, so I'd he we're hit by Toriko, he would die. I just see it more likely that it would be the other way around.