You're gonna have to use an impact wrench. When you use just a regular wrench, the interior part spins as well well when the nut is spinning. When you use an impact (even just a battery one will work) it will give it enough tourque to break it loose. That is how I did mine
i used an impact wrench, came right off. or, you'll have to rig something up. if you look inside the stud, there's a star bit hole, and you can get a torx bit (t45) in there. get a wrench around the nut, (obviously from the top, unless you have a recessed wrench that will get on there) or a pair of vice grips. you have to hold that torx bit steady otherwise the whole strut will spin. if you're doing it without hand tools, it's easiet to loosen it a LITTLE bit while it's still on the car. basically, just break it loose, and that's it because obviously if you take the nut off while it's on the car you're going to have a problem.