Screw the pedal back in the crank. Tap the key with a hammer, or use pliers to turn it in thr direction opposite to how you were previously turning it while holding the pedal with the wrench. Basically, you need the pedal to be solidly held so that you can apply force to the key, and the crank will hold it that way.
This. Screw it back in and simply wiggle it with your hand. You don't need penetrating oil, it's not corroded in place. You mechanically force-fit it into place. Now you need to reverse that. Use a hammer if necessary.