Honorable mention to Lil' Gotham which takes place outside the main canon even if Damian is more childlike than he normally is.
Old SPOILERS AHEAD
Damian greets Joker with a crowbar:
Do I need to say why I like this? Look at what Damian chose to use against Joker. While he's never had the warmest of feelings towards Jason just using a crowbar against Joker says a lot. He's making a statement. You mess with one of us you mess with all of us. It's him standing up for the Robin legacy, one of the reasons I'll never get behind the crap he pulled in Batman and Robin #10-12 vol. 2. Actions speak louder than words and this shows that he (at least at one point) respected what came before. What can I say? It's a good punchline.
I'm not talking about the one Morrison wrote about but the one Tomasi did in Batman and Robin #0. This one was one of the few stories that doesn't lay it on thick with Talia being some sort of monster. She still cares for her son even if she has that intense Al Ghul way of raising him. It explains why he's so obsessed with proving himself to his father and why Bruce disappointed him when they first met. While it does go overboard in making him a little badass it's worth checking out for anyone that's interested in reading more on the fourth boy Robin.
Bruce and Damian:
Bruce has had issues raising his kids. He always has and always will. This is a man that's not the best at expressing himself. That has and will continue to create problems between him and his family. He also hates killing for any reason, something that causes friction between him and anyone that takes a life. Damian has tried his whole life to make his mother proud. The man he grew up in awe of isn't as perfect as he was expecting. That made for some tense moments but slowly the two grew closer. Some have said that Bruce has never had a chance to be a father before, that his other kids don't count. I say that's bull. Little by little each of them has brought Bruce out of his shell. He cuts himself off emotionally when he doesn't know how to handle things. With Damian he couldn't because all Damian had was the family and Bruce knew he would be making the same mistakes he made before if he did.
Taking care of Damian gave Bruce insight he didn't have before. While I'm still not sure how the hell the Wingman thing came about I can get why Jason and Bruce are on better terms now. Their not perfectly okay but Bruce understands now. Just like he knew he had to not repeat the things he did with Jason he learned from raising Damian.
Alfred and Damian:
Like all bat kids Damian has a strong bond with Alfred. Likewise Alfred loves all his charges. True they didn't start off on the best of terms but Alfred kept his cool and won the littlest Robin over. Early on Damian even remarked that our beloved butler has acted more like a father than Bruce did (before Bruce turned things around of course.) What I find most interesting about this relationship, in terms of bat history, is the fact that Alfred has previously and privately blamed Bruce for another child dying under his watch. Since Morrison had Alfred allow Damian to go off into the battle that claimed his life it should make for a good story to see how that's explored.
Jason and Roy bond (or try to) with Damian:
Two different scenes from Red Hood and the Outlaws #17. Their both short but I like what they say about all the characters involved. I always thought various DC writers really dropped the ball on writing interactions between Damian and Jason. There was either bad writing at play or simply showing Damians' distain for his "brother." Not much to go on compared to the more complex relationships he has with Dick and Tim. Tomasi had Damian ignoring the things they share and wrote them in a way that hardly explored the rich potential they have. Morrison gets a little closer in Inc. by having Alfred and Jason give hints on how much the two have in common. But it's not much of an improvement. RHATO shows Jasons' pov for the first time and it really drives home why Damians' death is tragic despite it basically repeating Jasons' death. Jason sees Damian going through the same thing he did when he was Robin. He gets the weight of the legacy and the anger of a kid that wants to have a family that loves him. There's an attempt at reaching out to Damian in hopes that it's not too late for him that's ultimately rejected. It shows growth on Jasons' part and is tragic because Damian is doomed to suffer the same fate, even the same choices that lead to Jasons' death. It shows what could have been.
Despite Roys' past he's a lot more easy going than he used to be. He gets off on Damians' bad side when he arrives at the manor to pick Jason up and ignorantly assumes it's a safe house for Batman Inc. He doesn't take the insults the kid flings seriously and his dismissiveness on the threat level of a ten year old prompts Damian to suit up for a fight. Roy gets caught up in it until Jasons' exasperation with their behavior shames both enough to stop. The scene that follows with these two shows something Stephanie Brown introduced Damian to, the concept of having fun. It's Damian opening up to a stranger in a hearwarming way. Despite not having Lian in this 'verse Roy Harper still has the instincts of a father. All in all heartwarming stuff that would have been nice to expand on. Nothing in the book makes Damian a psycho, annoying or too bratty. His reactions are understandable without reducing other characters at the expense of his development.
Supergirl and Damian team up at Halloween:
There were a few people who not only won't put up with Damians' crap but called him on it. Super-Girl was one of those people. Admittingly he was a bit of an ass during this team up (like above when he mentions the Halloween stores not having costumes that were "street walker" like) but nevertheless this was fun. Full of funny moments and good character beats. Unlike others heroes like the Teen Titans (pre-relaunch since they didn't meet afterward) Kara made her feelings known without making Damian feel like crap. She didn't make him feel like he wasn't as worthy enough to be Robin. Kara may not have been thrilled to have him along but she accepted his help and relied on his skills. In the end that helped Damian feel more comforable around her. He would later team up with her and some other young heroes like Blue Beetle (Jaime Reyes) in a Supergirl arc. Apparently there were plans in the work to have them appear along side other heroes, perhaps forming a team, but that never happened.
Dick and Damians' partnership:
No I don't have any particular story or moment in mind for this one. Just Dick Grayson acting as a mentor for Damian. It helped Damian grow in a way that he wouldn't have if Bruce had been the one to take care of him from the start. The partnership also acted as a way for Dick to makes amends for past mistakes as a brother and honor Bruce by looking after his son. It was fun to boot. More so when you realize that an AU version of Damian got together with Dicks' little girl and Dick wasn't so approving.
It really says a lot when fans were willing to hold off of Bruce returning to the cowl just to have these two be Batman and Robin longer. Few people truly affected Damian as much as Dick. In a family that always seems to be at each others' throats during big events it's nice to see such a strong relationship especially since Damian had issues with legacies and adopted siblings.
Damian finds out how much Tim distrusts him:
Speaking of the issues Damian had with his siblings, none of them were worse than his rivalry with Tim Drake. He saw someone he had to replace to be Bruces' son and worst yet (for Damian) Tim wasn't willing to put up with it. At all. Usually Tim wasn't the sort to let people get to him but Damian was always the exception. Their fights mostly had readers choosing one of their sides but I think this one really showed neither were really in the wrong. Now at first I did feel for Damian but reading more of their interactions makes it easier to see both sides.
Tim made a list of threats based on who had to be taken out or who he felt was a threat that might need to be stopped. Damian hacking into the computer to find out that he was on the list. This made him lash out stating it wasn't fair since he was making a serious effort to improve himself. Tim never really felt comfortable around Damian, the way he acted or his methods. This tension never went away but was always interesting to watch.
Stephanie teaches Damian how to be a kid:
Dick might have been the one to really turn Damians' life around but Stephanie was the first one to realize that he needed to act his age. When she sees that he has no idea how to play with other kids she takes it upon herself to show him how to have fun. Their bond was a real gem to see. While she didn't put up with his crap she also realized that he was still a kid. Even Dick hadn't really realized that. Stephanie did have to defend herself from his attack but it was much more playful than the fights with Tim. In fact you can pinpoint Damians' exasperation with her when Stephanie meets him and accidently freezes him to stop a fire. He enjoyed taunting her and got to see that you don't need to be broody to do the job. Trying to spread hope and improve one' self are just as valid. I found it interesting that Damian felt the need to pick on her so much from the start. As he says he wanted to know what made her tick. At the end of her run Damian respected her and she--while occasionally annoyed--was fond of him too.
While not one of his siblings I think Stephanie was the one that had the most sibling like relationship with Damian. There was teasing, playfulness, and a lot of little details that were overlooked with his adopted brothers and his brief meeting with Cass.