Having some time to reflect, while it is emotionally powerful, this finale makes no sense. It basically boils down to this:

Aquakind: we are gonna melt the ice caps

Humans: no pls we will drown

Aquakind: lol skill issue

Humans: fine then we will kill you first

Aquakind: no why did you kill us we surrender

Humans: we are monsters

So i guess the moral of the story is: Humans are awful, Aquakind are awful, and if you litter, Kate Lethbridge-Stewart will come after you with a gun, so don’t.