Wow, that's a mess. Looks like the incorrect tools were at work there. If you have a welder you could weld a nut onto that then you could use a 6 point socket on it.
I would remove the wheel, drill the head off, and remove the caliper. This should leave a "stem" of the bolt where it passes through the fork lower that should be enough to get purchase with vise grips.
Hard to see if there are any edges left with all of the corrosion. Maybe chisel and brush the corrosion off and see if a 6 point socket ( hammered on ) can get a hold on it?