Unchained

Alastor hasn't had any scenes to indicate that he genuinely cares for Charlie, Angel, or Vaggi beyond that he finds them entertaining and/or useful to an extent.

He has with Niffty, on multiple occasions.

And something that I think is important about his relationship with Niffty is that she actively makes it clear she cares about him in return.

She's the only one who's been shown going out of her way to help him with no (apparent) strings attached, and is openly affectionate.

With everyone else at the hotel? They've either largely ignored him or only come to him when they need something.

He had to make a deal with Vaggi just so he could be assured that he wouldn't have to participate in something he hates (TV) again after he helped her with the second commercial. They could have easily asked him to advertise on his Radio Show, but instead went out of their way to make him film a video commercial. Hell, they could have even just asked him for filming equipment and done the actual filming theirselves considering their only guest at the time was Angel Dust. Their schedules weren't exactly busy at that point in the narrative.

Charlie barely cared when he was captured, focusing more on her social media war with the Vees than on the fact that he was, as far as she was aware, kidnapped. Vaggi was even less concerned (although her reasoning for her lack of concern was understandable, and she was right that he was planning something).

When he and Emily get hurt, Charlie runs to Emily, the one she's known for maybe a few weeks in universe. Not Alastor, who she has been living with for over half a year and frequently relies on.

His seemingly genuine friendship with Rosie is marred by the fact that he was in servitude to her for nearly a century. Meanwhile, he is to Husk what Rosie was to him. Same issue, different font.

Sir Pentious was only interested in him because he wanted to prove himself to the overlords by beating him.

The only times Angel has spoken to him was to flirt (as far as I can remember). Cherri and Baxter meanwhile have had little to no interactions with him.

Mimzy, his only known friend from his living life, is a white woman who frequently uses his care for her to her advantage. Essentially treating him like her own personal attack dog. Mind you, this is a friendship that posed the risk of getting him killed simply by association due to the time they lived in, and it's implied she had him doing favors for her anyway, which would have increased that potential outcome significantly.

Vox, while he had genuine feelings for Alastor, still tried to team up with him to use his powers for his own benefit, and waited until Alastor was at least slightly inebriated to shoot his shot.

Alastor is somewhere around 130-150 years old, and the only times he's been shown genuine care (as far as the audience is aware atp) is from Niffty, Emily (who went out of her way to try to save him), Husk when attempting to warn him about Mimzy, and likely his own mother. ...That's a very small number of times for such a large time span.

Everyone else wants something from him, and they don't hide it at all.

None of this is to say that Alastor is justified in his more negative behaviors. Dude is in hell for a reason. But I can't really blame the guy for treating almost everyone else like pawns when they more or less do the same to him in the grand scheme of things.

Considering that "an eye for an eye" is a running theme in this show, I wouldn't be surprised if Alastor only begins experiencing "positive" character growth once someone begins treating a relationship with him (platonic or otherwise) as something other than transactional.

Presently, I can only see Lucifer and Emily being able to fulfill that need.

From what we've been shown thus far, Alastor doesn't have anything material that Lucifer objectively needs, aside from potentially being his executioner. (Which he could make a deal with literally any number of powerful sinners to do. Alastor isn't inherently special in this possibility).

Emily, meanwhile, isn't the kind of person who would develop a friendship with strings attached.