Not really a "fandom", but Science Fiction. My two most controversial takes:
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In Alien 3, Hicks and Newt had to die in order to thematically be an Alien film. Alien (the original trilogy) was always Ripley's story; a woman who has had everything taken away from her and ends up an outsider where the only real touchstone left to her is the very xenomorph that she battles. In Alien, she's an outcast among the crew. In Aliens, she's a civilian amongst a bunch of mega-macho mercenaries. In Alien 3, she's a female among male prisoners. Thematically, Ripley simply can't have an ensemble cast around her at the beginning or the end of each film. Fincher understood that.
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In Blade Runner (before future movies retconned it), not only is Deckard a replicant, he's a very specific replicant. Gaff was the original Blade Runner on the case, and he got wounded in the leg during the escaped Replicant's first attempt at getting into the Tyrell Corporation. Supposedly one of them got fried going through an electric fence, but in reality, that replicant was captured and reprogrammed with Gaff's life; Gaff's memories in order to continue the investigation. Meanwhile, Gaff himself is forced to babysit this "replacement" that everyone else thinks can do just a good a job as he can, and so he's bitter about it through the whole film and taunts the replicant with cryptic hints about his memories.