The MCU has Thanos, arguably the most iconic villain since The Joker in The Dark Knight. Thanos is endlessly quotable, and lends himself to a lot of memes, and his presence single-handedly justifies the epic near 6 hour sojourn into comic book mayhem that Infinity War and Endgame collectively represent.
Star Wars has Chancellor/Emperor Palpatine. Now, Darth Vader is the more "immediate" villain, but Palpatine is the true bad guy of the series, orchestrating the fall of Anakin Skywalker, and ruling the Galaxy behind the scenes. Palpatine is also endlessly quotable and memeable, and the rise of prequel memes has given a new lease of life to his endlessly quotable dialog.
Which one do you think is more memeable/quotable?