Originally Posted by LesterOfPuppets

I've tweaked a few. Bench vise + Crescent wrench, or hammer + garage floor, then fine tune with a park Derailleur hanger alignment tool or by screwing a 10mm axle of a rear wheel into the derailleur bolt hole and eyeballing things.

Hammering on them or bending them back does increase the chance of complete hanger failure, but I like living on the edge.