Nutec bolt-off works a lot better than PB.
If traditional methods don't work, call up a friend to help.
You'll need an impact wrench and an air hammer.
Install a pointed bit on the air hammer (like a center punch) and then position the bit directly over the center hole of the bolt on the nut side.
Use the impact wrench on the other side to turn the bolt while the air hammer is pushing the bolt out.
If the quad is on a stand without anything else holding the swingarm on or you're some kind of spiderman/stretch armstrong lovechild you can do both at the same time.
It takes a good amount of time to really get it loose enough to remove, and you may have to use a long center punch if it gets hung up halfway through.
Would probably be a good idea to replace both the swingarm bolt and the bearings if it's that difficult to remove, but at the bare minimum at least replace the bearings.
The reason I recommended using the center hole on the bolt is just in case you somehow can't remove it, or the bolt itself is fine once you get it out...then the bolt isn't a completely lost cause.
Repeated bashing against a nut covering the threads of the bolt will still damage the threads, so try to use that as a last resort.