This question rised while I was making a fan-fic were the Kingdom Hearts characters are important, but 0 Disney. I'm not an expert in Warner Bros franchises, but I know a bit of DC, so I could develope better for that case.

Worlds I think it could have:
Looney Tunes
Lego
Beetlejuice
Wizarding World:

• KH 2/Days: Harry Potter and the Prisoner of Azkaban
• Birth by Sleep: Harry Potter and the Philosopher's Stone
• Dream Drop Distance: Order of the Phoenix
• KH 3: Deathly Hallows
• Union χ: Fantastic Beasts

The Hobbit
All the Hannah Barbera IPs
Clash of the Titans
Matrix
Willy Wonka
Teenage Mutant Ninja Turtles
DC:

• KH 1/Chain of Memories/Re:Coded: Batman: The Animated Series (final boss: The Joker)
• KH 2/Days: Smallville (final boss: Darkseid)
• Birth by Sleep: Christopher Reeve's Superman/Michael Keaton's Batman
• Dream Drop Distance: The Death of Superman (final boss: Abomination)/Batman Beyond
• KH 3: Dark Knight Returns/Snyderverse (final boss: Ezra Mill-, *ejem*, Darkseid)
• Union χ: Arrowverse
• KH 4: Injustice (final boss: Superman)/Crisis on Infinite Earths (final boss: Anti-Monitor)

Dune (KH 4)
Monsterverse (KH 4)

Darkseid surely would be a recurrent villain.