The angle grinder, die grinder, Dremel tool, all would be alright. Just as Tony pointed out you would be best to immobilize the screw & nut from spinning before grinding, or just a hacksaw to cut the thing.
I have a chain nose vice grips which I would attach to something like this to stop it from turning. A bungee cord holding the vice grips in place and use my die grinder, that seem easy enough.
I had a front wheel axle that I used a regular vice grips to stop from turning while a cross threaded nut was preventing from taking the thing apart. Sometimes stuff happens, and things your about to fix, need additional things to fix in the process. Just get creative, but wear ear plugs, face mask, & face shield that covers neck area. Goggles are not going to prevent something like a cut off wheel fragment from ending up in the esophagus!
I use my die grinder with a separate speed control, this so I get a better control.
The bike itself could also be immobilized by using some cord or bungees. I used my old lead weight belt or heavy chain and bungees any time I use the center stand with one wheel off the bike. A stand that grabs and holds the frame still, I never got that fancy to buy the like, but improvised what I have works.
MT