Tickle Monster - literally

My son is the WORST tickler on the planet and, unfortunately for everyone who comes in contact with him, he loves to tickle. When Z takes a running start toward you and says "tick, tick, tick, tickle!" you know that is your cue to run. His tickles hurts indescribably bad. I have cut his nails down to the nubs but it doesn't help. The receiver of his tickle torture inevitably ends up looking like they got into a bar fight with a cat. His horribleness is special in that it isn't just the nails, it is the amount of force he puts behind the tickle as well. He digs his little fingers so far into you that I'm surprised he hasn't ripped out someone's organ.

I feel really bad because I always have to discipline the poor kid for tickling which, in most cases, is a normal cute kid thing to do. I have to sound like the meanest mom ever in public when I punish him for tickling his sister. Of course if I ever get a dirty look from a stranger, I'll just sic Z on them and then they will understand.

His little face is always crushed when I get mad at him for it. He is just trying to be sweet and goofy and playful but it isn't normal to have to take a trip to the emergency room after being tickled.

The whole situation reminds me of this episode of friends where Monica gave the worst back rubs and they were extremely painful to everyone she tried to do them to. She was just trying to be nice by rubbing people's backs. Finally she took pride in being the "best worst back rubber" on the planet and she quit doing it.

Not sure how to explain that concept to a 2 year old.