Assuming you're talking about the drive side pedal then it is the right hand threaded side assuming the pedals were correctly installed by whoever did this. Since I can't see a bike shop installing them wrong or cross threaded it would appear that some previous owner did indeed take up the challenge at some point so any combination of mistakes is possible. If it's a cheap pedal then the spindle may well be bent so it'll LOOK like it's cross threaded but really it isn't. If it truly is cross threaded and driven home and you're turning it the correct way then my own feeling is that you'll find that the crank arm is toast. Once a pedal is driven home completely cross threaded then the only cure is either a heli-coil or other such thread repair or to toss it and buy a new part.

Chasing threads does not restore the original metal, it just cuts away more metal. Chasing is only good for threads where they were just started crooked but where most of the thread is OK and you're just trying to clean up the first few turns. A fully driven home cross threaded pedal will have ruined the threads.

Try heating the arm with a propane torch to exand it. Direct the heat mostly at the aluminium and let it travel along the arm to the pedal end by conduction. That should allow you to turn the pedal out and see what the situation really is.