Best type of villain? 

Aizen - Was pretty much unbeatable. Bland character with no backstory and a shikai that would make a 4 year old girl look immensely overpowered. To top it off, his plan was boring as crap. 

All DBZ antagonists in the beginning of an arch - Do punches and powers, they do nothing. Some dumb shit training + Get pissed off for new magical form = Same techniques but evil guy is like OMGWTF and get punched. Then failed Genkidama. 

The thing with these bad guys is that you know the protagonist (or one of them) would have to shit out some even more stupidly powerful ability which makes you think how pointless character development is in these cases. Goku gets moar muscles all of a sudden, Ichigo comes out of the closet with his sword and suddenly becomes God. 

So yeah, asspulling endings there. 

A good Antagonist: Meruem. Well developed, he didn't appear unstoppable while keeping a very dominant role, just very clever and was obviously quite strong. He was still hard to kill but we pretty much knew all about his goals and how he was this strong. No ass-pulling.