as above get a big breaker bar. it will also help if u get a chisel to knock out the 'staked' part of the nut.
if you take the wheel off you will see a section of the nut that has been' staked' into a cutout on the cv joint to stop the nut from coming undone.
try using some heat also it may have been cross threaded at some point.
I've never come across an rst with a left handed thread so undo it in the normall way