I have some vice grips that I use for that. Name brand w/ the straight teeth (not curved), and I notched a bit into the teeth to hold the nut better.
Clamp that b!tch down hard and tap the vice grips with a small hammer to loosen.


* I didn't even replace that brake line fitting after that (all metal line), just coated with anti-sieze and put it back on with the vice grips.

__________________
1985 300TD 1981 Scirocco 1.6D conv 1986 Golf 1.6D 2003 Golf TDI