The most underrated anime that you have watched?

I don't know. That series seems to be pretty highly rated whenever I see it on sites like MAL and whatnot. It's just not as well-known as most mainstream series. For me, something like Boogiepop Phantom or Shinkai Makoto's short She and her Cat (not the ONA short series although that was good as well).

I actually made a post about this anime just yesterday. I love all the story telling methods they employ in this series. Squealer is low key the most evil fucker to have ever been created. Even right to the end, this anime makes you stand on end questioning everything about the world they're in. (The ending where they analyze the DNA of the Monster Rats is just nuts)

Bokurano, It's like a less edgy Neon Genesis Evangelion, but also not at all. Tbh I can't explain it, just go and watch it, I dunno

Shinsekai Yori is actually one of the most well known anime in the west. Most underrated for me would be kamisama no memochou, and Ergo proxy