Kira and O'Brien didn't have a romantic relationship, did they? IIRC, it was an attraction which they were able to work past in basically a single episode without acting on it.
T'Pol and Trip. Not because they made a bad match or I didn't want them to get together, but because they telegraphed they were going to force a romance right in the decon scene in the pilot.
There was an (uncomfortable to watch) attraction between the two. Given that Miles was not the most attentive husband to Keiko or father to Molly on DS9. The sudden injection of a budding romance between Miles and Kira (with the back massages, Miles helping Kira out of baths, the planned trip to a relaxing romantic spot on Bajor, Kira living with the O'Brien's quarters), had me thinking "Why even go there?". Just like the Chakotay/Seven relationship. Why did the creators even go there during their final hour? Seven the most popular and arguably the most developed character on VOY is paired with Chakotay. Chakotay who is one of the least possible and least developed characters on the show.
Yeah, I get you with Kira and O'Brien: why even think about going there, is how I would put it. I agree. Chakotay and Seven, though, they actually went there, as did the other two couples. I'm voting Kira & O'Brien and T'Pol & Trip. They're both in a league of bad distinctly worse than the other two. At least the other two couples had something resembling a normal relationship.
Easily, for me, it would have to be Jadzia and Worf. Last we knew, Worf and Troi had a budding relationship going, that could easily have still been going on long distance, but suddenly he falls for someone that much older than him, and that has been a man on several occasions (when ALL we've ever seen Worf interested in is women)? The whole thing just seemed out of the blue and out of character for Worf. Of course, I'm biased, because I never really cared for Jadzia in general, and I really don't like Riker/Troi (even though I have to admit that that pairing at least makes some sense), either, so....
Jadzia was a woman. With memories of male past lives, yes, but I don't see how Worf falling for her goes against his alleged heterosexuality. I'm no fan of that relationship, but their gender identity and orientations have nothing to do with it. Kira and O'Brien is mega cringeworthy. Kira and Odo didn't work for me either. Chakotay and Seven is the worst. It didn't work, and is a taint on the whole series for me.
Chakotay's crush on Janeway, definitely. The aching. The longing. The yearning. Especially when Q wanted to have a kid with her, because she's the MOST desireable woman in ALL of the known galaxy, apparently, Chakotay embarasses himself by telling her he was emotionally upset over it. Who is Janeway to Chakotay, even at this point? Their friendship wasn't even on the level of hers and Tuvoks. It was just embarassing and definitely mirrored Nurse Chapel's crush on Spock, from the original series. AND.............to the same result, as a matter of fact.
Kira and O'Brien seemed stupid. At least all the others, good or bad, looked like something. Plus none of the others were clandestine.
I was never big on Worf and Troi. Just didn't see a lot of on screen chemistry there. By then I think everybody was getting tired of being jerked around on the whole Riker/Troi relationship. Throwing Worf in there was the death knell for that concept. By the time Riker and Troi were married in Nemesis, noboby really cared about them anymore.
I was glad that Troi and Riker finally got married, but their story was dragged out too long. I was rooting for Tom Riker, out of disgust that Will kept running away from love for so long. Imzadi II: Triangle did give resolution to Worf and Troi and continued developing Will and Troi.
What would have happened if the Dax symbiont had been placed within a male host after Jadzia's death? There was a bare chance that Worf and Ezri would have been a couple, but I can't fathom Worf being in a same-sex marriage. Even in the most bizarre fanfic I've ever read, I've never seen anyone do a same-sex marriage/partnership between male Klingons.
There's a strong Klingon warrior with a Klingon doctor husband in one of the Enterprise novels, with no suggestion of homophobia in Klingon culture.
Yeah, the Troi/Worf pairing really didn't come out of the blue. There were several episodes in which a bond between them was developing, but it was a slow build ("Parallels" in particular showed an alternate reality in which they were married, and it was kind of after that they became an actual couple). They seemed to split off-screen after Worf was assigned to Deep Space Nine or maybe even not long after the loss of the Enterprise-D. Heck maybe even his losing of both the Enterprise and Troi may have contributed a bit to his decision to come to DS9.
Seven & Chakotay. Yes in that it came from absolutely nowhere, but more because there was actually an episode focusing on those two characters together only three episodes before Endgame (Natural Law) and there was zero indication of anything then. The opportunity for the writers was there, but as usual on the show they seemed to squander it.