This shit happens to me all the time at work. Since my narrow little ass only weighs 150 lbs. soaking wet one must get creative sometimes.
Heat and a BIG FUCKING CHEATER BAR.
If It’s real bad you may need an extra Bubba or two.
If it still refuses to budge you get out the Smoke Wrench and order a new fitting.
I’ll never forget the time me and a buddy were trying to break loose a two inch nut with a breaker bar and that fucker wouldn’t budge. We were underneath the main floor with steel grating and big I Beams overhead.. I went and got a strap and a Come Along, we wrapped the strap around the breaker bar, hooked the Come Along up to the beam and winched that fucker loose.
I don’t like to lose.