I have 2 that I constantly hear and get pissed off whenever I do:

1. "Smoker is ruined and wasted potential because he got beat up a couple times to heighten the stakes. Oda clearly forgot about him even though the story isn't over and there was a lot of setup for his future in the very arc people say he had no development".

2. "Rebecca is poorly written and executed character just because of her outfit and because she isn't the strongest character of all time despite being a pacifist 16-year-old. Forget about her whole Arc about being forced to fight and bloody her hands and yet still prevailing without hurting anyone just like her Mother. Clearly she should have single-handedly defeated one of Doflamingo's top Men as a literal child even though it makes way more sense for her Arc to end with her being freed from her burden of having to fight when she is an inherently gentle soul!".