I would nominate Dagny for acting on her emotions in the face of immutable facts. She should have sold out her Taggart stock converted it to gold and "shrugged". There is no way to win against statists who use the government to help them, and James Taggart and his friends were going to win and destroy anything she did.

My #3 most loathsome character was intended to be a hero: Ragnar Danneskjold. He was a villain to me because he was a thief. He claimed to steal only from the looters and give to the producers, but life is never that clear cut. Most people pay some taxes and get money from some stupid gov't program at some point, and that doesn't make them consummate producers or looters. It seemed like his point was the looters didn't respect property, so he wouldn't either, modeling himself after the looters. All thieves have a justification. His was tu quoque. I did not like him.

My #2 most loathsome character:
Jim Taggart was close behind when he became abusive toward his wife for seeing herself as human being equal to him or anyone else. He needed his wife to feel like a diamond in the rough, not quiet worthy, who should always count herself lucky to be affiliated with him.

His evil also showed when they were torturing John Galt and seemed to lose sight of the goal of co-opting Galt and instead just wanted to see him suffer because he was good and that made Jim feel bad.

He was an evil little $#!& through and through.