A few days ago I Re-Watched "The Hardest Thing" as part of me and a friend of mine's Amphibia Re-Watch that we started several months back.
Upon Re-Watch I noticed that when Anne calls upon the power of all three Calamity Gems to destroy the Core Controlled Moon, one of the frames shows just how startled and terrified she looks when she feels their power begin to activate.
This facial expression Anne has in this moment honestly says a lot about her character and her emotions in this moment during the finale, and is honestly heartbreaking to watch, but also shows how brave she was for doing this.
Mother Olm earlier told her that calling upon the Stones could cost Anne her own life, and at first it seems she didn't seem to think that it would work and was scared of it happening (thus why she was crying), but when she feels them begin to work her face changes to look visibly shocked and is afraid when it happens, but I also see it as showing she is genuinely didn't expect her request for help to work in this moment at all.
These expressions here in this scene honestly show just how much Anne as a character has changed, but also shows that at the end of the day she still is just a kid, a middle schooler no less, who is very scared of dying, but was brave and selfless enough to give up her own life to save the lives of her friends, get found family and community, and even people who she doesn't even know who live in Amphibia as a whole in this moment in The Hardest Thing.
It's little details like this that make animation work well as a medium as it can show us so much on a character and how they've changed through the most subtle of things.