My Shimano pedals finally needed replacing after 25 years of use. They had never been removed since fitting and at the time I didn't have any Copperslip grease available.
First pedal was removed with difficulty using a long spanner and a large hammer.
The other pedal (chainring side) refused to budge at all, even with overnight soaking in releasing fluid.
Applied heat to the pedal/crank area with a blowlamp. Still no luck using a long spanner and a bigger hammer.
Eventually, removed chainset from the bike and stripped down the pedal so that I could hold the pedal spindle in my bench vise.
Found a 5' length of 2x2 timber, and using five toestraps, attached the timber to the crank and spider. Didn't attach to the chainrings, due to the risk of buckling them.
Pushing heavily on the end of the timber resulted in the crank slightly undoing from the pedal spindle. After that, I was able to undo the rest of the way by pushing and pulling on the chainrings.
This time, when fitting the new pedals, I made sure to apply Copperslip grease to the threads.