Do you think Tezzeret is capable of positive relationships with people he cares about?
I think it's clear that he's capable of deeply caring about people and tries to influence them positively. He has character flaws that make that kind of relationship difficult, but gets better with time.
In Agents of Artifice he is trying to have a positive relationship with Jace, but he, like Jace, thinks he knows what's best for others, thinks he understands them more deeply than they understand themselves, and will use force to make what he thinks is best for them happen. Tezzeret sees a lot of himself in Jace and has empathy for him, he is trying to force him onto the path that he thinks would have been right for himself if he were in Jace's position. His forceful training and punishment is an attempt at a positive constructive relationship. At this point, he wasn't capable of doing this in a way that didn't involve force because he just wasn't emotionally developed to that point.
In Test of Metal, his aggressive edge is somewhat softened and his care for others is able to more fully shine through. He improvises a plan on the spot that risks his life in order to save Baltrice's. He also clearly cares deeply about Doc in that story, and even though Doc is an extension of himself, he forms a positive and constructive relationship with him that is in turn a positive relationship with himself.
“No,” I said. “I want to beat him.”
“To save Baltrice?”
“And myself. And you.”
“I don’t get it. Seriously. We can just sit here. Bolas’ll show up to kick us out again, and he can broker a deal with Vess, and we’re in. Crap, Tezz, we might be able to get Bolas to step on Renn—that way we don’t get the snot beat out of us. Or get killed.”
“Baltrice doesn’t have that much time.”
“So?” That brought me to a full stop. So indeed. “Don’t you like her?”
“Do I need to remind you that she’s tried to kill us at least once already this week?”
“To protect Jace,” I said. “She can’t help it. I don’t hold it against her.”
“Well, I do. Let the fat cow die. Our business is Crucius.”
“We need Baltrice,” I insisted. “We need her.”
“Oh, I get it,” he said. “Whether I like her doesn’t matter. You like her.”
I frowned. “Apparently I do,” I said slowly. “But that’s not the issue.”
He also saved Baltrice from Jace, made sure she had the option to know the truth about him, and defended her from him. If he had done that only to get back at Jace or control him in some way, I think he would have done it very differently - it was about Baltrice and making sure she had the option to live the best life for herself.
Skipping forward to Edge of Eternities, it seems to me that he is developing a positive, constructive relationship with Sami and cares about them. He is more outwardly gentle than he was in previous interpersonal relationships and talks jokingly with them - this is further development from the way he spoke with Baltrice near the end of Test of Metal. He talks jokingly with Sami and calls them pet names like "Child Captain" and "Boy". Sami feels comfortable enough to have a secret nickname for him as well while working for him.
There are a few interactions that I feel like demonstrate their relationship is positive, appropriately friendly, and working for them.
The intercom chimes. "Hey. You two. The Metalman's here. Come out and present yourselves, or he'll present you. And by the way, please don't call him Metalman. Or tell him I call him Metalman. He prefers the name Tezzeret."
The description of Tezzeret from Sami's point of view is also interesting for this:
He pushes into the Seriema with the calm of a prybar. There is nothing hasty about him. He crackles with pent-up potential, with ungrounded charge. The air smells of ozone and bitter oil. He is like the clouds on Uthros, pregnant with lightning. Sami has seen the black carapace of his body open.
His head is human, though strange. Strands of white hair drift in zero gravity. His neck vanishes into an armature of ciphered, dark metal, immune to any inspection. He is shaped like a man but would be insulted by the equation, "Tezzeret is a man." He would laugh at how it lessened him.
Clearly they know him as intimately as it is possible to with the relationship they have.
I think that, coming from his educational/apprenticeship background and his relationship with his father, he has a built-in need to mentor people who he sees something important in. When he sees someone who can come up the way he did, not quite rags-to-riches like him - but get somewhere from where they are, he tries to sculpt them into that. His methods have been harsh and coercive with several people... but I think with the slight change of heart/gentleness he has developed, the right person could be very receptive and have a very positive experience being cared about and mentored by him.
Also, even with the very, very negative things he did to them, Jace and Baltrice gained valuable skills from their time working with/being mentored by him that changed their lives for the better.
