Pics would be good.
This should be able to be straightened up and using decent sized tie-downs should do the job. A better option might be a cable winch as used on 4WD recovery, but try the tie-downs first.
You need to set up with in a way to make sure you do not over step the effort and cause more problems - you need to have some bracing in the opposite direction ie: the to place a limit on how much you straighten at each time and not allow any chance of moving too far the other way.
As with all straightening levelling etc the trick is to take things carefully and smoothly and to fix off at each move ie: straighten say halfway then tie off to make sure it can't move back. Once you have the ends perpendicular you can use diagonal cross bracing (steel bracing or timber) to hold it in place.