To be honest, unless it's part of a very long piece of track, I'd be inclined to just scrap that bit of rail.... OK, you might not want to waste a 4 foot length, but if it's just a 2 foot or 1 foot piece then I'd recover the sleeper bed and the one good rail for possible re-use if you find another damaged length anytime, and put the bent rail length into the "spares box" for cutting into short bits at some point.
The suggestions of cutting the whole thing into two short track sections either side of the bent bit are also good.
I don't think you'll ever really manage to get that back into the correct shape, and the time and hassle spent trying would (for me, anyway) outweigh the cost of getting another length of track to replace it.
Jon.