Even without Nightcrawler acting viciously out of character and teleporting people's heads off, I still give Kurt the win here.
He's leaps and bounds ahead of KD in terms of skill and I don't buy that Kid Devil is durable enough to not be hurt at all by punches and kicks. Plus, there are lots of other things Kurt can do like grab KD and teleport around, making him dizzy until he passes out. Back in the day, teleporting with Wolverine was enough to leave both him and Nightcrawler unconscious because the ride was so rocky. With his current skill level, Nightcrawler can teleport people without this happening but by choice he's been able to make the ride rough enough to hurt the other guy.