Imagine downvoting other people because they don't want to call a fictional character with your preffered gender pronoun. Poison was trans. Biologically male, but modified with female parts. So you can call them with both genders, as fictional character won't object nor possess any sentience to protest. After all, their genders could be modified as the artist likes. Yes, we tag with what we see, not what we know, but there's no rule not to misgender a trans based on how they look.
Imagine downvoting other people because they don't want to call a fictional character with a gender that fits your belief. Poison was trans. Biologically male, but modified with female parts. So you can call them with both genders, as fictional character won't object nor possess any sentience to protest. After all, their genders could be modified as the artist likes. Yes, we tag with what we see, not what we know, but there's no rule not to misgender a trans based on how they look.
Pretty sure if the creators say a character is female, that makes them a female. It literally doesn't matter what Poison's birth gender is, nor is "tag what you see" even remotely relevant here. We still wouldn't tag her as male even if we did prioritize canon tagging, because officially she's female.
Insisting on misgendering a fictional character, despite all official sources designating them as female, says a lot about how you really feel about the idea of transitioning. It's clearly nothing to do with the character, because you have to go out of your way to do it, when you could just not.