I really liked Rumpelstiltskin, he was funny and terrifying at the same time

Lord Farquhar was the most interesting because he was the only villain not originally from Fairy Tales and his past is unknown (I don't count the plays as Canon) . It would have been cool to see a flashback of how he rose to power in Duloc

The godmother was great and her song was iconic . Outside of stiltskin I think she was the most powerful villain in the series, I wish she was seen in the Alternate world in Shrek 5

Everyone says Charming was the weakest villain but I thought he was cool. I did like his monologe to the villains at the bar in Shrek 3, it was my favorite scene of his in the movies. I wish they would bring him back in 5 because it never showed what happened to him after Shrek embarrassed him during the play and he got stuck under the tower prop