The ‘parents guide’ section of any given movie on IMDb tells you what to look out for in these films. My kid saw these but not all can.
Boy (a New Zealand film)
Anime to watch while you’re still a kid
Wolf Children and Grave of the Fireflies are also great but the latter in particular is very sad. Wolf Children is probably more sad for adults than for kids.
Kickass older teenage girls
We Are The Best! (Swedish, and hard to find)
Films for adults which a 12-year-old would probably understand
True Grit (either the old or the new one, but the dialogue in the old one is easier to understand)
What Maisie Knew
Boyhood (it’s long, needs an intermission)
Gritty but good for discussion:
Into The Wild
Samson and Delilah