Going by the description in canon, it makes you feel everything you've ever made someone else feel. So if, say, Vanora got hit with it, she would feel the pain one of Serrill's bullies felt when she punched him in the face, but she would also feel Serrill's relief and sense of being protected.

Huh. That's pretty interesting. I suppose the next question is to what degree are figures in authority considered to be responsible? Galbatorix is high king. The buck stops with him as far as anything happening the Emprie goes. Does that mean he's responsible for the pain his soldiers feel when they execute his orders to defend their homes from invaders and lose? Does that mean he's responsible for the agony someone in a small village feels because there aren't enough painkillers available and Galbatorix could theoretically have improved supply lines so there would be some available?

Granted, though, Galbatorix has personally killed enough people and made enough Name-slaves that the spell would cause him ultimate pain however his role as high king played in or didn't.