Mai trusting Ty Lee's "aura sense" in order to guage the trustworthiness of a NOS pasty she is dating in order to get intel (despite already knowing who their leader is and one of their hideouts)
Mai initally honeypots said pasty also to get back at Zuko, but eventually falls for him but he breaks up with since it is painfully obvious that she still simps for Zuko
Zuko trying to get into Mai's pants while searching for Azula's crew, despite the fact it is largely his fault that Azula is free and Mai (and Ty Lee) rightfully fear for their lives (and Tom-Tom's) (pic related)
Azula getting a very unjustified/unearned power-boost that allows her to slap all of the non-AS powered main characters without really trying once she regains her "sanity"
Azula regaining her "sanity" but deciding on a 148D plan to make Zuko into a tyrannt when there are better ways off doing so like becoming his advisor
Ursa telling Zuko to never forget who he is but mindwiping herself of her time at the palace despite meaning she loses the memory of her kids
Ursa writting a letter saying that Zuko isn't Ozai's kid. Ursa knows that she and Zuko only have value if Zuko and Azula are Ozai's kids so if Ozai was smart, he could have used the letter to kill them off. Moreover, it makes Ozai stupid; instead of burning/banishing Zuko or trying to kill Zuko on DoBS, he could have released the letter to the public, essentially disinheirting Zuko without ever getting his hands dirty.
Western-style straightjackets and mental asylums; modern wheelchairs and forklifts
Sokka getting reduced to comedic relief for the most part and Toph's powerlevel being inconsistently portrayed in order to maintain tension in the various plots she is involved in