Drill a hole for a screw extractor but the drill bit keeps breaking.
Use a wrench to bench the fender flange back into place (images 2 & 3)
Cold chisel to try to make a flathead screwdriver able to fit in the bolt head. My chisel wasn’t cutting in too deep. I might try this again but on the side and really knock the screwdriver with a hammer tomorrow.
Is the point that you need to remove the fender? Take a grinder to it, and then just rig a new way to secure the fender when it goes back on. It’s just holding a body panel, not securing a head gasket or something.
You pound the socket onto the damaged bolt head. Then as you try to loosen the bolt the flutes in the socket grab the bolt head tighter the more you turn to loosen it.
Looks like the bolt is basically not securing the fender anyway, I see the bolt turned sideways in the middle picture, just move it back and forth and it should pull out nut and all pretty easy… lol
If you are not removing the fender then just leave it be, you may be opening up a can of worms…
I’d probably use a dremmel cut-off wheel to make an “x” in the bolt face, then start the drill at the center of the “x” and drill the bolt out. Bolts like that are pretty soft steel, doesn’t take much to drill them out. If your drill bit is breaking, it is either dull, too small diameter, or made from weak steel. There’s a big difference in the materials drill bits are made of, expensive to less expensive. I have several types, and the less expensive set of bits break all the time.