So you want a legit villain as a LI?
I think it would be interesting if said villainous LI was a NPC who was part of an enemy faction. Perhaps he (since you would like it to be a male) is much more affable than his fellow baddies and shows an interest in the PC during a battle. They then develop a secret romance unbeknownst to the PCs companions. They have private LI scenes and conversations, but at the same time they still fight against the PC in public since they are on opposite sides. Something like that?
A villain companion might be more difficult to pull off without risking them becoming an anti-hero. Still interesting, though.
Kind of. They don't necessarily have to be against the PCs goals in most scenarios however (since I know that'd probably be more difficult to implement). I don't mind whether they're a companion or not whichever is easier to implement is fine with me *shrug*
Yeah my thoughts for a antagonist LI mainly had them as a villian similar to Loghain (not in personality so much but more of a human threat and preferably sane). Maybe they can be a NPC you meet and certain dungeons/scenes go differently depending on whether you've befriended/romanced them or if you ignored/antagonized them in disguise.
Could be a bit of a run spin off the typical tropes like villian leaving you in a lousy dungeon (perhaps that only happens if they're friends/lovers with the PC) otherwise you get someone who's clearly a dangerous and fearsome opponent and your PC barely escapes alive. Little twists like that could add flavor to the romance.
But mostly I just want an LI that's not gonna give me a frowny face for choosing the renedouche/assquisitor/kick the puppies and laugh choices. While being intelligent and without a crappy past excuse.
But...Anders, Isabela and Fenris all kind of fit that description, depending on the route you take with them? Especially Anders, oh my god.
They're all woobies (especially Fenris). All of them have sad pasts that serve as a sort of reasoning for their behavior. Anders saw the abuses of the templars and wanted to free his fellow mages, Isabela got sold by her own mother so she tries to shrug off attachment, even the slaves was a mistake she didn't want to repeat. And they're not that villainous. Isabela tries not to care about other people but she does she's good at hiding it most of the time, Anders got into most of his situations because he cares about people other than himself even if DA2's ending had him stuck stupid (Note his horror at the slaughter when you reach the docks. Awakening Anders might've fit but that's not who we got in DA2), and Fenris is just a jerk towards mages and those who support them because of his experiences in Tevinter.
That and Fenris and Isabela both suffer the want to become a better person syndrome. (On that matter I really want that LI not to be someone the PC wants or can "fix")