What have you tried so far?

If you can't get a breaker bar on it while the car is in 5th with the brakes depressed, try soaking it in PB blaster first. Try getting as much leverage on it as possible.

If all else fails, take it to a tire shop/mechanic and I'm sure they won't mind zipping it off with an impact gun and tightening it just enough to get it loosened when you get home.