Trollhunters
I discovered this series while browsing something on Netflix Kids with my kids and after finishing the first season I already knew it was going to be one of those jewels that you absolutely love.
Both me and my kids waited with anticipation every new season and now that it's ended I sincerly have that bittersweet feeling of something good that ended but that couldn't have ended better than this.
I strongly recommend everyone to give it a watch, either if you have kids or if you just love animation's movie. It's really something special.
The series is completed (spoilers in this article) as stated previously, several time, by the creator Gulliermo del Toro and this just proves how it was a labour of love instead of a milking machine (looking at you How To Train Your Dragon").
Also some info about the two upcoming spin-off, 3 Below and Wizards.
Netflix: https://www.netflix.com/title/80075820
uNoGS: https://unogs.com/video/?v=80075820 (seems to be available everywhere)
IMDB: https://www.imdb.com/title/tt1734135/
Rotten Tomatoes: Season 1 - Season 2 - Season 3 - Average 95%