Very true, a long hard push is what's needed. Since it has only been bent once with a single blow, in theory a single anti-blow in the exact opposite direction should straighten it perfectly. If you want to hammer it, you'd need a hammer the size of a small car. Rather than trying to generate that force using kinetic energy in a short sharp shock, a long slow torque will do the same job. I have noticed this effect when straightening massive vice handles in the flypress. All the effort goes into setting it up, then just give it a bonk. The metal will "want" to bend where it already has and I surprise myself when a single firm shove makes it ruler straight in one go!