Just lock the crank by any of the methods above and put a few feet of leverage on it.

You just arent being brutal enough with it, its not something that needs treating delicately.

Swiss Tony says:
Removing your crank bolt is very much like making love to a beautiful women.
You need to make sure its well and truely locked in place and cant move, then you need to be as brutal as possible to it with the largest tool you have available and as many of your mates as possible to help you.