It will depend on the grade of the steel as to whether this will work with stainless steel. Some will be so tough that you just won't bend it, and some can be brittle and even snap. This would be an easy job with mild steel.
If it is already threaded, your next biggest problem is not wrecking the threads during the bending process.
If this is a length of ss threaded rod from a builders merchants or similar, then it will be cheap enough to have a gamble with. I would clamp between two pieces of scrap wood in the jaws of a well secured engineer's vice on a strong bench, and place a putlock (c 4 foot long piece of scaffold tube) over the exposed end (with the thread well wrapped in cloth).
Then grunt a lot, and sweat a bit, and push a bit, and you may persuade it to go somewhere near where you want it. If you resort to hitting it with a lump hammer, firstly, you will have to protect the thread somehow, and secondly, you will have to dampen the springing effect. The hammer and steel will just bounce around a lot. You need to hit it very near the bend, and not out on the free end of rod.
Best of luck.........what are you making?
Mike