In reality tho, this is less of a MCU thing than a comic book movie thing in general. There are significantly less occurrences of repeated villains in any comic book movies some there existence. The rare few that even do resurge are almost always no longer the true villain of their respective series either. More often than not, they are either regalated to dead spirit flashback status (Green Goblin of OG Spiderman trilogy, Raj Al Ghul Nolan trilogy), turn semi-maladjusted, anti-hero (Loki) or straight up background status cameo appearance (Scarecrow Nolan verse again and he never was even every number one villain in any of them). Only Magneto of the X-men movies ever was consistently a number one villain and even he was among at least one of those other tropes before as well and their shenanigans continuity almost doesn't make most his recurrences even count.
You could say that Joker, Green Goblin and Two-Face had repeats, but then you literally have to stretch universes to count those, lol.