If you are talking about the big axle nut, often, there is a groove in the axle and once the nut is installed, they crimp it into the groove, so it can't back off. This is a PITA!! I usually have "decent" luck using a breaker bar and a 3 foot cheater slid onto that. This makes about a 5 foot wrench and so it is easy to get 2-300 ft lbs of torque to bust it loose.
No offense, but if I remember you correctly, you are a fairly light weight guy, it may help you to find yo' self a fatass to put some weight behind the attempt! I would be more than happy to help, but you couldn't afford my gas to come from Seattle!
If you know a mechanic at a shop, it may be easier to just have him do the job, since it is about 2 hours to R&R an axle. Plus, they have a lift so it is easier to work on!!
Good luck!