(based on their personality and things they've said)
Characters who I think care about their Pokemon as friends/partners: Cain, Victoria, Julia, Corey before all the bad stuff happened to him, Shelly, Kiki, Radomus, Luna, Adrienn, Amaria, Hardy, Taka, Lumi, Anna, Laura, Bennett, Cal in the present, Arclight
Fern to an extent. Ame on tumblr replied to an ask about how Fern treats his Pokemon, and she said she imagines he would play favorites, as in ones that do well would be used more in battles, but that he wouldn't abuse them if they lost.
Characters who I think use Pokemon as a means to achieve their goals: Corey after the bad stuff happened, Titania, Saphira, Lin, Solaris, Sirius, Eve, Zero, Sigmund, Cal when he was just trying to prove himself to his brother, Blake
P.S. I still think it's kind of jarring seeing Titania swing her Aegislash against a wall.
Ones I'm not sure of:
-Florinia. I think before she tried to purge her emotions, she probably cared. Now it's kind of hard to say, but I imagine bonds became secondary to things like strategy. Also, the real person who was Florinia in the online league wasn't even interested in Pokemon and was only there because of her friends (Julia, Amaria, Titania), although I'm not sure if that's ever going to carry over into the game.
-Shade. Anna says he's nice, so that's promising, but we don't really know much about him.
-Aya. She uses Cain's Pokemon that he left behind, so it's unclear if she was a trainer before then, and we don't have any indication of how she treats them. Based on her personality I'd say neutral at best, and at worst has some hard feelings from being reminded of Cain from them. (although in Agate Cain and Aya did talk out their issues somewhat)
-Serra. She's a shell of her former self, so we haven't seen much of a personality from her. Considering she gave up her modeling career for Bennett and took in Luna, I'd like to think she does care for them.
-Noel. He doesn't really express emotion so it's hard to tell, but I'd like to think he does since he has a Clefable, and Cleffa evolves into Clefairy through happiness. Although evolved forms of baby Pokemon like Pikachu and Clefairy can be found in the wild in Pokemon games, seeing as he has a Cleffa doll I think it's more likely he raised it from a Cleffa.
-Samson. I think as of right now he's the least developed character in Reborn, and at least to me doesn't seem to have much of a defined personality.
-Charlotte.
-Terra. She could probably create hacked Pokemon.
-Ciel. Based on her personality I'd think she does, but like Samson she hasn't had much screen time.
-El. While he did use Ditto as a means of achieving a goal (turning people against Radomus), I imagine he might consider Pokemon as Arceus's creations and thus consider it wrong to mistreat them.
-Heather