Worst MTB injury

Nothing like yours I suspect.....two moderately bad ones.
1/ Misjudged a step up, front of crankset hit the step stopping it rather abruptly, slid forward over the front of the bike and went over to the right, left upper arm was across the end of the bar as I landed and the brake lever went into my upper arm by about an inch. Rode back to the car park (last 5 miles of cannock) in severe pain, couldn't lift my left arm, had to use my right hand to put my left hand on the bars. Couldn't change gear in the car so my Son changed gear all the way home (32 miles - he was 16 at the time), in A&E they said the brake lever had almost severed a muscle group in my upper arm and put in in plaster to immobilise it to protect it for a week.
2/ High speed open trail at night on leaves (autumn), wasn't familiar with the trail, found myself having to turn when crossing a wooden bridge, front wheel washed out and I slammed into the ground chest first, pretty sore, couldn't breath deeply so the last 5 miles was spend shallow panting like an Alsation on a hot summers day, saw the nurse the next day (unrelated) and diagnosed as two broken ribs, was off bikes for just over a week, then on road commuting and then back on the MTB 3 weeks later.

Nothing as gorey, but over the bars resulting in fractured elbow.
Hospital initially said it was just badly bruised, put arm in a sling and told me to keep it elevated for 24 hours.
I was only told it was broken when I went back after two months as I could still not straighten my arm.
Ended up having four months of physio before scan and consultant then decided surgery was required.
Had a further five months of physio after surgery and whilst it is better, I still cannot full straighten the arm
It is now elbow pads for every ride

Couple of broken ribs and a bruised coccyx plus I hit a gate in the lakes and when I went over the bars I whacked by balls.
They swelled up and went the colour of beetroots.

Two broken ribs managed to pedal back to my van somehow,took about 5 months before they settled enough to be able to lay on a surf board again,2 broken bones in my hand not sure what was worse,the injury or the £750 Bill in a Swiss clinic,had a bad off in Led Gets one year landed on my back going feet first,can remember trying to push my feet down to stop stones and gravel going up between my body armour and skin,couldn't walk properly for a couple of days, still convinced had it not been for the armour I probably would not be walking now

A broken rib on two occasions and a torn shoulder. All on the lefthand side, so that must be telling me something.

Been pretty lucky - riding MTB since 1995 or so and while I've collected the usual scrapes, scratches and pedal bites, I've only had three 'serious' injuries.

About 5 years ago, had a silly little off on a local drop and cut my knee. didn't seem too bad so finished the rest of the ride. Got home and showered - the second the water hit my knee I was in agony. Peered down and could just about see kneecap at the bottom of the hole that was now washed clean. Did the stupid man thing and though it would be OK, plastered the wound closed and that was that. End of the next day at work I could barely walk on it. Went to the doctor who said it was too late now to stitch it so it would have to heal naturally and steristripped it closed. eight weeks later I could just about bend it enough again to ride. No idea what I actually did but knee still clicks on and off when pedalling.

Mini enduro at FoD - OTB on the Corkscrew resutled in a couple of cracked ribs and a couple of weeks of agony if doing anything other than just sitting and gently breathing...

This spring went flying over the bars off a little drop on Coal Not Dole at BPW. Though I'd got away with it but arms were both too sore to carry on riding. Went to A&E with a mate that afternoon for his knee injury but didn't get an x-ray as (stupidly again) assumed I'd be OK. Two days later back at home it wasn't OK - got an x-ray and Radial Head Fracture kept me off the bike for 8 weeks again.

EDIT. Like the poster a few posts above noticed, these were all on my right side. I'm left handed so there must be some vague ability of slef-preservation at play somewhere?

Still reckon I've been pretty lucky over the years though.

Not sure. Think it was stage 2 maybe 4 years ago. It's a 180 right hand hairpin that then dives 90 degrees left and steeply down a rooty chute.