In cases like these, I use a motorcycle tyre-iron. Wedge it in between the crankarm & fixed-cup with the tip of the iron aimed at the crankarm. Pry towards the seat-tube and >POP< off it goes in 2-3 seconds.

Of course, depends upon how much exposed spindle you have between the crankarm & fixed-cup. With larger clearances, I've used a pickle-fork, used to separate automotive A-arms from ball-joints. Both methods causes minimal damage to crankarm and it can be re-used if you want.