Late to this thread but I'l add this for posterity at least. Used to dirt bike ride which of course lead to many curled up clutch and brake levers. Tried many times to carefully/gently straighten them out with no success, they always snapped off immediately. One day took a different approach, put the lever in a vise, applied just a very small amount of heat from a propane torch and gave it a couple of moderate whacks with a hammer or leather mallet and the lever straightened out with no problem. Since then I've used this method many times with good results.
If you think about it makes sense since it got bent into a pretzel with a sudden impact and so reversing this works best. Do not heat to get it smoking hot, only enough to warm it up a little.