I've had success removing the drive side crank with the fixed cup and spindle still attached. Remove adjustable side first. Then carefully remove fixed cup with a wrench behind the crankset.
Once you have the drive side removed (with the fixed cup and spindle still attached), use a drill press to drill out the cotter pin.
I also have a nice cotter press, but it doesn't always work.
The remove first method always works as long as you can remove at least one side of the crank (drive or non-drive side).
Once it is removed, you can also apply brute strength at will.