One of my favorite arcs is the S season, especially because I LOVE the Outer Senshi, the dynamics between Usagi and Haruka (and the fact that it's confirmed that Haruka is gender fluid), ChibiUsa and Hotaru's friendship (and maybe more, because it's hinted by Hotaru that she has feelings for ChibiUsa AND I SHIP IT SO HARD) and the whole Sailor Saturn arc (I love how powerful she is and she's the Senshi that represents my star sign, yay!). It's an exceptionally dark arc in the series, and it's even darker in the mangá. Takeuchi doesn't shy away from certain things and it ups the stakes for our heroines. Also, Mamoru is much more present here and it's more useful than in the anime. It almost makes me like him as much as Seiya & Haruka.