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Omg! If there’s a welder, just blob a little bit of weld until you have a bit sticking out and as @lynx says weld a nut through the hole to that. The heat will have released the bolt and it’s a bingo. 60% of the time it works every time.
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Might be better to reply @Light_EDDed not me.
The bolt is not siezed in, 'just'overtighten. So looking at ways to get the bolt out. So welding a bolt in the drilled hole will either get the bolt out or break the weld or break the bolt. Even if the bolt breaks easy enough to remove.
Personally I'd try widening the hole with a drill, to make the hole conical and hammer a torx bit in. So the edges get some bite in to the bolt. Using an impact driver will hopefully give it the incentive to move.
In that case, weld a smaller bolt in to the hole you have drilled and then unscrew.