Favorites:
Deen: Definitely my favorite character overall, likely because Shura was one of my favorites in Fates and they're pretty similar. I love his first interaction with Celica when he's being recruited (characters giving other characters nicknames is an immediate tick on the like scale for me, lol).
Saber: For all the obvious reasons, Saber is just a total badass. They took the drunk sellsword trope and made him incredibly likeable with how much of a big brother figure he is towards Celica.
Mae: Sure, I'm still hyper! LET'S GO!
Leon: He manages to be a sweet sassmaster while still being very mature. I adored Virion and Inigo in Awakening so I guess it's no surprise that I'd also like Leon.
Zeke: He isn't really an /Echoes/ character per se, but I am attached to him and all of his alternate identities from throughout the games, and I still like him here and think he's a very cool character.
An honorable mention for Forsyth because I think his voice actor had a lot of fun with his goofball personality, and I chuckle everytime I hear him say "Ha! Step aside!"
Least Favorites:
Faye: :put_litter_in_its_place: emote from Discord is exactly how I feel about Faye. I mostly dislike her because Silque just wanted a cute friend and she was sbshffjref so rude.