As a trash bin raider, I get this problem all the time.
If I can't remove a pedal with a wrench and a few hammer taps, I soak it overnight with penetrating oil and try again.
If this doesn't work (and you are willing to trash the axle):
1. remove the pedal cage leaving just the axle on the crank arm 2. drill a small hole in the center of the axle on the crank end 3. drill progressively larger holes 4. file parallel flats on the other end of the axle. 5. grip the flats with a vice grip or wrench. 6. unthread
By drilling a hole in the metal "under" the thread you are weakening the "pressure" on the thread.
This takes time, but works without damaging the chrome or the arm in any way.
Amir Avitzur
Ramat-Gan, Israel