Not sure if you mean structurally damaging, disturbing, or physically painful...
The most painful thing I had happen was several years ago on my wrestling team during practice I shattered my toe into 3 separate pieces, and 5 minutes later had to (and did) sprint 4 km while staying ahead of coach.
Needless to say, when I got back from practice my entire foot was red-purple and the toe was so dark it looked black.
Most disturbing was when I slammed a bare toe into a concrete curb, split the toenail into 4 pieces, and for reason I never understood, the blood didn't spray or pour, just exuded like soft serve from hell.
Structurally was one that wouldn't actually seem that bad. I jammed my right ring finger in a match and just blew it off, but when it didn't get better (and by better I mean swelling decreased, not less painful) I went to get it checked out and x-ray'd. Turned out, I popped a thin splinter of bone out of the side of the joint, which left a hollow gap in a part of the bone that is supposed to be really strong. Had I hit it again, the bone would likely have snapped off sideways, and I would have had a finger like an upside down L.

silly satanist!

Why didn't u tell him?

To that question I give the answer I give to everyone who asks why I don't react to pain.
Because
I'm not
A pussy.

not because u lack one of the five senses?

I was 8 or 9 years old, and where on the playground in school, and there was some kind of climbing wall and i was nearly up there, and then i slided off and felt down, exactly on my elbow, it breaked (Wtf verb form O.o) and now i can put my elbow in many directions which normal people cant do :3

i think u are looking for "broke"

That is disturbingly cool....

I was riding my dirt bike in eastern Washington and rode up to this really steep incline, normally this wouldn't be a problem but this was the first time I had ridden since the year before (can't ride in the winter). I was a little rusty on my inclines and forgot to never use the front break on a hill. I ended up flipping the bike over and sideways with the left foot peg impaling my calf. Not only did that hurt like a bitch but I had to hop onto the back of my dad's bike and ride home to get in the car and get operated on. My left leg is now about an inch thinner at that point when compared to my right.

My story:

Blades and I don't get along...

Me and some friends were messing around with fireworks (problem 1 sighted) and we got bored (problem two sighted). So we decided to put some firecrackers into a tennis ball. Well, to do that, we would have had to cut the tennis ball open. I had an old folding pocket knife that my dad had given to me, and so I was like "I'll just push down on the top of the tennis ball and pierce it, the cut the rest of the slit". Well, while the blade of the knife was sharp enough, the tip wasn't all that great, so when I pushed down, the tennis ball just compressed. Thinking that all it needed was a little extra power, I put my body weight over top the knife as I stabbed downwards.

Well, long story short, the lock of the folding knife gave out, and folded the knife back in on my hand with nearly my full bodyweight behind it.

It cut through everything but bone. I started pouring blood out everywhere and almost passed out from losing so much by the time I got to the hospital.

Luckily, my friend's dad is a reconstructive surgeon that specializes in hands, and he fixed me up real nice. I have a nice scar and a couple numb spots on my hand, but other than that, I'm fine.

But man... that sucked so bad.

Well, should be my broken arm in Norway when I was on holiday there. After that I had to walk two hours through the forest until I could get into a car and to a hospital.

Umm... Probably when my dick got cut off D:

lol jk, probably when I spiral fractured my leg and it span around 3 times and like yeah, it was all fucked up for like a year :/

Tis all good now.