Previous PR villians...
Well the four groups from OO weren't too bad, Flurious was improvement over Gayja but Kandor wasn't as good as Yaiba so that's pretty much a wash.
The Master/N'Ma are about even, Neither was actually a physical presence until the very end of the series. N'Ma did more then 'The Master' but The master's possesion of Nick and the subsequent knock-down drag out brawl between him and Leanbow was AWESOME so I can't complain too much.
Grumm, slight improvement over Agent whathisname but not anything worth writing home about.
Mesogog... Started scary but got progressively dumber as the season went along with his weird ass plan of the week to return the planet to the time of Dinosaurs.
Lothor, I LOVED Lothor. He was and remains MY FAVORITE NZ villian. He had the best personality, the best lines. Oh he was funny AND memorable. Not a great character design or anything but he good everywhere else.
That's just my .02 on the bad guys though.