A while back, my YZ125G swingarm bolt was fully seized in.
I soaked it in all sorts of stuff for days.
I used a propane torch to continually heat the area.
I was lucky that one end of the swingarm bolt had a hex head where i could get an impact air driver on and continually work on it forward and reverse.
I used a Hilti to continually hammer on it.
The combination of heat, lube, hammering, torquing and time eventually started to gradually turn and move it mm by mm.
After a few days of continual work, it came out. The bolt was ruined of course, but everything else was fine.
Cheers,