I'm not sure what i think of Damian in a relationship. I always see him ending up like 666 Batman with his cats just due to his lifestyle and who he is. [the weight of The Batman and The Al Ghul legacies reduces the chances of a happily everafter]
His past experiences and the experiences of those around him when it comes to relationships no doubt have left scars and shaped his outlook. Damian will likely be even worse than his father at relationships.
I like Damian and Kara in Injustice [there too he's oblivious to her fondness of him]
I like the idea of him and Alexis Luthor from The Just though she betrayed him and it was hinted that he had feelings for Chris Kent the universe's Superman. i would have liked to see more of that world and that relationship.
There was also Kingdom Come where he's with Mari Grayson. I really, really love the idea of Damian ending up becoming Dick's son-in-law [is that too creepy?]
I even like the childhood teases with Maps and Djinn but I think he will be unlucky in love.