Big Meme and her crew, ESPECIALLY them coming to Wano.
Overloading Wano with 10,000 characters.
Most Post TS antagonists, Doflamingo's crew in particular was a huge disappointment.
Doflamingo shifting from a Joker type villain into a clone of Crocodile with a god complex.
Kaido becoming the King of the Hostages in his fight with Eiichiro Oden.
The Great Cake Chase.
The Rikus and the Dwarfs.
The Kozukis and Toki the plot device/McMuffin.
The time travel twist, really don't think we needed it.
Kyoshiro being Denjiro.
The growing chosen one bullshit revolving around Luffy.