Tribbie's interesting enough, but there's a lot of tropes she shares with Nahida in Genshin- and Nahida did most of those tropes better, in my personal opinion. Mydei is neat, but it felt like he kept going back and forth between an elite berserker and a fusion of Proto Arthur and Iskandar/Alexander. He did find his footing by the end, and they did it in a way that I actually enjoyed a lot... but at the same time, my initial iffy impressions meant he never really hit my heart. I think it was the repetition of his parents'/comrades' deaths that ruined it for me.
Anaxa, from my current point in the story- after the confrontation with Aglaea in front of the Council of Elders and reveal of the Coreflame/Titan inheritance cycle, but before we meet Cipher and head to Styxia- is fantastic. Lelouch vi Britannia meets Edward Elric, with a little bit of Hoyo's preferred flavor for sassy smart aleck boys. His dynamic with Cerces is wonderful, and his practical, logic-based approach to (most of) the workings of the world around him is just straight-up refreshing.
Castorice is another who just doesn't really appeal to me, but she is still interesting. The dead twin angle is... probably going to bore me in the second half of 3.2, I'll be honest. But everything else about her, including the twist reveal of our ability to interact with her- the fact that it's not because we're special, but because we're dead lmao- that was good. Made me reconsider half the stuff that happened since we landed on Amphoreus, and more twists like that are honestly what I'm hoping for- that's probably why Anaxa is so interesting to me.
So far I think Anaxa, the Black Swordsman, Aglaea and Phainon are the most interesting characters in the story for me- in roughly that order.