Weld a nut onto the top of it. Should be able to accomplish this with a MIG and a steady hand
Cut a slot in the top with a rotary tool cutting wheel, use a large manual impact driver to crack it, or a dull chisel/flat punch and a hammer to tap it around (clearance might be an issue here)
Rotary tool again, cut faces on two sides, locking pliers, turn them with channel locks
Rotay tool yet again, cut faces on six sides, hammer a possibly sacrificial six point socket on it
Last option is rotary tool again, grind that head clean off. If there’s enough exposed shaft after the part removal then turn with vice grips. Hopefully you used brand name Loc-tite.
Otherwise its screw extract time. I suggest Micro-grabits. Only reliable option IME.
How many torques are on that?
Ideas:
I like you, you’re a good human. Saving this for if/when it needs to be replaced in the future.
Last option is rotary tool again, grind that head clean off. If there’s enough exposed shaft after the part removal then turn with vice grips. Hopefully you used brand name Loc-tite.
Otherwise its screw extract time. I suggest Micro-grabits. Only reliable option IME.
Apply some heat to the bolt with a tiny tiny torch to hopefully not damage the aluminum nearby? Should help release the threadlocker.