Put the BB socket into a vise and put the frame on top of it. Turn the frame. This gives you massive leverage. So much leverage that you had better make sure you are turning the bike in the right direction, otherwise you will cross-thread the BB and then you have a new problem.

If you don't have vise, use a breaker bar. If you don't have a breaker bar, use a normal socket handle with a pipe over the end of it. But the vise is the best bet in terms of not slipping.