About 15 years ago I bought a nice Athena Triple and fitted it to my Randonneur using SPD M-520 pedals to turn it, well the pedals are definitely killed now and it has taken me 3 months of on/off attention to get them off without harming the cranks. The winning formula was to apply heat with a butane gas torch then a goodly spray of Halfords Shock and Unlock penetrating oil (I think its actually isopropyl alcohol, it boils off really quickly) and a little spray of WD-40 then wait some time before repeating after standing on a suitably sturdy pedal wrench. I'm 16stone - which helps btw.
So, happy day - I managed to get both pedals off and the lithium teflon grease had turned to chalk dust and now I'm pedal shopping
Also the penetrating oil is really good at cleaning oily/greasy stuff -and evaporates off without any residue.