About 4 months ago, I had a pedal/shoe fitting on my hybrid.The LBS did the pedal install.
Thinking about selling the hybrid, as I have bought a roadie. Went to put the stock pedals back, the right one is seized - yes I know they are handed. The pedal is so seized that my Park pedal tool is rounding out. Any tips? Really would hate to mutilate something.
Penetrating oil, gravity, and time. Use a lube like PB blaster or true penetrating oil, lay the bike on its side, apply lube a couple times a day over a few days. Leverage also helps; find a way to lock the crank arm while applying force to the pedal.
One thing you might try is to take the crank arm off. after that find a vice and put that sucker on there. Chances are that you will be able to exert a bit more pressure on it that way.
Is it possible that you might have installed the wrong pedal? I've done that myself on customers Bike and had to rebuild the threads within the insert. lucky for me the process works pretty well and I haven't gotten any complaints from him yet.
The main problem I find with petals is that inserting a threaded steel shank into aluminum whole. Added to that, most petal wrenches will give you an awful lot of force which can make things go bad fast.
What I should do is to thread the pedal in with a standard wrench or just my fingers and then use the big wrench to tighten it down. Its kind of hard to cross thread of pedal with just your fingers.