OK, this one is for future searchers.
I wa an idiot and hammered on the very end of the axle WITHOUT the nut on the end (hint, don't do that!)
Result? Of course, bent threads slightly right on the very end.
I couldn't get the axle nut to go back on, so what to do?
Basically, either go buy another halfshaft, or try to fix it.
I used an impact wrench and tried to just "power it on", that didn't work, only resulted in slightly screwing up the nut as well. I tried using a dremel buffer tool on the end to try and bring out the definition of the threads, tried using a cut-off wheel to deburr and accentuate the threads, neither worked very well.
Next step was going to be cut it off with a hacksaw past the bent threads and then deal with repairing the threads again.
Then, I had a stroke of genius (for me).
I took the axle nut, which was already somewhat screwed up anyway, and used the dremel cut-off wheel to CUT IT IN HALF.
Yep, that's right, cut it all the way through on one side, flipped it and held it right on the cut with a pair of vice-grips, then cut it on the other side.
Let the nut cool, and then place it carefully back on the axle threads, use the 32mm socket back onto the cut nut, careful to hold it together when you slide the socket back onto the nut. You want to place the nut down past the bad spot, I put it about halfway down the shaft. Use the impact wrench in reverse, and spin the nut back off the axle. I had to repeat this 3x, and the impact was working at it to get the nut off. Next, put the good nut onto the axle, and use a good socket or tire-iron to get it back on. It will be tough, but just keep at it, and it will go all the way on. when it passes the bad spot, it will spin easily. You may want to reverse it again close to the end then tighten again.
Voila! You just saved buying another axle!
What is needed:
Dremel with cut-off wheel (I used 2, but have plenty on hand if you get too aggressive with it)
32mm deep-well socket
Another axle nut.