Lego Joker!
Probably has the best Joker plan of all time, very in tune with his emotions and pretty funny.
Magneto.
Not sure how you're going to react to this cause I know some people are getting tired of Marvel movies ending with a battle between a super hero and super villain who have the exact same powers... but my favorite Super Villains are literally characters who are evil copies of their Heroic counterparts.
Bizzaro, Reverse Flash, Sinestro, Negaduck, Venom.
I do think it gets a little repetitive and boring when a hero has more than one evil counterpart. Reverse Flash was the original we didn't need Zoom, Savitar, God Speed, ect and it makes the Reverse Flash seem like less of a threat when there are multiple evil speedsters.
Optimus Prime even has multiple evil clones now. Motormaster who's been in the G1 cartoon and Robots in Disguise 2015. Scourge who was an evil version of Optimus Prime exclusively in Robots in Disguise 2001, great character but calling him Scourge was really more of a name dump since the original Scourge had nothing to do with Optimus and every other character who's used that name has had nothing to do with being an evil Optimus Prime. And then we have Nemesis Prime which is the best name for an Evil Optimus Prime clone but depending on which version you're looking at there's never been a consistent origin for this character. The first Nemesis Prime was from Armada and he started out as Sideways before randomly turning into an Evil Optimus clone for ONE EPISODE and then turned back into Sideways... and also he's kind of also Unicron... that series was horribly dubbed from the original Japanese Micron Legend so a lot of it doesn't make any sense what so ever. The show was rushed out in America while it was still being worked on so the American release also has incomplete animation and a lot of errors that were changed in the Japanese version. We later got another Nemesis Prime in a series titled Transformers Prime which was a human built transformer that didn't have a spark piloted by a human villain named Silas. Nemesis Prime wasn't really a character since it wasn't sentient so for all intent and purposed Silas was Nemesis Prime. The Nemesis Prime robot again only appeared in one episode before being destroyed and Silas himself was also nearly killed in that episode. Silas has a lot more appearances and I actually love any episode he's in so highly recommend that one. Movie Nemesis Prime is actually just a brainwashed Optimus Prime, only time that Nemesis Prime and Optimus Prime are literally the same character. Only appears as Nemesis Prime in the Last Knight. Actually wait... I almost forgot in the Netflix series that Nemesis Prime was also the same character but he still gets to fight Optimus Prime due to some time traveling shenanigans but yeah Netflix Nemesis Prime is basically a future version of Optimus Prime who had been corrupted and changed by Unicron in the same way that Megatron became Galvatron. There is also Shattered Glass Optimus Prime who is from an universe where the Autobots are the villains and the Decepticons are the heroes. And Toxitron who as far as I know appeared in one animated comic book where Optimus had arrested the real Toxitron and disguised himself as Toxitron because they share the same body type with a different paint scheme. Oddly enough there was also a Motormaster in that comic though unlike the G1 cartoon they actually address the fact that Motormaster has a different head sculpt and Optimus can't be made to look like him with just paint.
I should also mention Megatron himself was an evil Optimus ONCE in Beast Machines when he built himself a copy of the Optimal Optimus body but with his face and no beast mode. And for some odd ball reason despite the fact there are now three different official versions of Optimal Optimus, one of which is missing his beast mode, and a couple different third party figures based on the design which are already missing the Maximal insignias for Trade Mark reasons, not one of them has thought to remold the face to make it Megatron. That version of Megatron has never had a toy despite being an obvious retool of existing figures and it still annoys me no one has made it happen. There is one custom out there someone made but it's not like that person is mass producing them so I can actually add one to my collection.
WHAT IS WRONG WITH YOU PEOPLE?
There is only one "best" supervillain. Everybody knows that.
Edit: whaddya mean, who? It's Dr. Evil. It was always Dr. Evil.
@CuddleDuncan: Oh. Well, you've got me there.
Dr. Evil forever!
...Good villains are like excellent desserts. It's difficult to choose just one to be your favorite.
Totally agree with that statement you found @MissAdventurous
Enigma/Riddler from the tv show Gothom
@CuddleForDID I really enjoyed CWs Flash, most of the time, but yeah, since the only thing that can basically beat a speedster is another speedster, it had to get repetitive unfortunately. Reverse Flash def the OG best villain within the show for sure.