Last time I had this happen (stuck plug that is, compliments of the Toyota dealer), it took a 1/2 drive deepwell socket and a long breaker bar. Took over an hour of steady pulling to get the plug out 1/8 of a turn at a time. Rachets mave give and not allow the transfer of energy. When the plug came out, it brought the threads with it (aluminum head).
This was on the wife's ride, and she last had the plugs changed at the dealer. Consensus is the plug was cross threaded.
Best of luck to you.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.