Heat.
Hammer.
Repeat.
Sixdogs gave good advice - clamp it solidly in a vise, then heat with a torch to cherry red.
You will be able to straighten it by hand (wear heavy gloves!) or with some gentle hammering.
Thanks, thanks to thee, my worthy friend,
For the lesson thou hast taught!
Thus at the flaming forge of life
Our fortunes must be wrought;
Thus on its sounding anvil shaped
Each burning deed and thought!