But, he is a main character in the franchise, even though he's a villain. Batman and Joker are a bit different, Joker is one of many batman villains, but in Transformers it is Optimus and Megatron as the story leads in most cases, reacting to and against each other. To have one gone feels incomplete. Megatron isn't just another two-bit villain of the week, there's a reason he's stuck around so long. Even in the TMNT/Shredder example, Shredder is just as much an integral part of their story, just as Megatron is to Transformers. It's not like he needs to be the absolute forefront of everything, but as for the movies he's been less and less relevant, and being completely absent in 2 major films, with barely any roles in 4 and 5. The last time we had a Megatron/Galvatron vs Optimus fight on screen was in Age of Extinction, before KSI whisks him away when lockdown shows up. In Last Knight they exchange 1 set of lines before Optimus kicks him out of the ship or whatever, and before that, the last fight was in RotF. In Dark of the Moon Optimus just runs up and rips his head off in a few seconds, Sentinel and Optimus get a longer fight. I'd be in agreement if Megatron was an integral part of each of the films with memorable moments and fights... but he really hasn't been. So it feels weird to me to be jumping around to other wannabe villains like Quintessa and Scourge, when we can't even do Megatron proper once.