God, where do I start?
The hot loner guy who never spoke to anybody and generally behaved like a jerk? Falls flat for the pretty girl who ends up discovering he is the most sensitive man EVER.
For that matter, any guy the heroine hated the guts of and fought with every minute- ends up being the love of her life.. Especially if he was a childhood friend who grew up with her.
Millionaires are sick of their money. And the people around them. And will always fall in love with a pretty woman simply because she is "natural" or "truthful" And might additionally decide to quit and enjoy a peaceful life (like they couldn't take vacations in private islands when they were rich!)
Actually, any good-looking well-to-do guy will always fall for the common girl-next-door (however annoying or stupid she might be and how much she might have screwed up his image socially with her gaffes) simply because she is "truthful" or "real".
The nice guy who was the heroine's best friend and who you were supposed to think of as very sweet? Is actually a psychopath out to kill her and destroy the world. But guess what? Underneath all that evil he would still do anything to make that heroine happy and is madly, oh-so-madly in love with her.
The bad guy who kills/loots/does a lot of despicable criminal stuff? Has a sad miserable past and STILL misses his mother.
The protagonist can solve problems with common sense or basic school level science that experts in the field couldn't. (I think this one idea helps them sell the story as screenplays to Hollywood!)
All the powers of a superhero are in one small object that can be easily stolen.
All wars or other big fights should end in a one-on-one combat.
Any prophecy made by any fortune teller would turn out to be true.
If your renting agent said a house is haunted and you tried to be brave and said "Bah, Humbug", 2 days after you move in you will find blood stains on the carpet.
Kids who are like 6 or 8 year olds can solve mysteries that adults can't. From all sorts of Enid Blyton style adventure novels to harry Potter's first few years at Hogwarts to Narnia to everything else.
Anyone who passionately loves ANYthing is actually better than the best in the world in that thing.
And many more. But above everything else..... The fact that there is a single villain who is the cause of everything wrong with the world.