FYI, not counting variants from What If, YFNSM and Zombies, counting each Season of shows as separate project and including confirmed future appearances
Uatu the Watcher-6 projects (What If season 1, 2 and 3, I am Groot, YFNSM, Eyes of Wakanda)
Daredevil-5 projects (Spider-Man No Way Home, She-Hulk, Echo, Daredevil Born Again Season 1 and 2)
Bucky-4 projects (TFATWS, Captain America Brave New World, Thunderbolts*, Avengers Doomsday)
Yelena-4 projects (Black Widow, Hawkeye, Thunderbolts*, Avengers Doomsday)
Loki-4 Projects (Loki Season 1 and 2, Ant-Man and the Wasp Quantumania, Avengers Doomsday)
Valentina-4 projects (TFATWS, Black Widow, Black Panther Wakanda Forever, Thunderbolts*)
Kingpin-4 projects (Hawkeye, Echo, Daredevil Born Again Season 1 and 2)
Punisher-4 projects (Daredevil Born Again Season 1 and 2, Punisher special, Spider-Man Brand New Day)
Wong-4 projects (Shang-Chi, Spider-Man No Way Home, Doctor Strange in the Multiverse of Madness, She-Hulk)
Everyone else has 3 appearances or less.