Princess Mononoke
Didn't quite hit as emotionally hard as I expected it to (pretty much cos I expected to be traumatised with animal deaths) but the animation was incredible and it did such a good job of not having a simple "boo evil humans destroying environment bad" plot, Lady Eboshi was a very nuanced villain.
Can't believe this is rated PG in the UK though, I was shooketh when someone gets dismembered like 5 minutes in