Now, I'm not talking about characters that were bad in themselves, just bad together.
1. Worf & Jadzia.
One of the things I really appreciated about Riker and Troi is that there were short moment here and there about them but it never became too much of a melodrama and they never got involved with each other again in TNG series proper.
IDK what it is about Worf, but the ST writers kept trying to pair him more than anybody else. First with a Klingon that was cynical about anything Klingon (but way cooler than Torres could ever hope to be), but unfortunately that pairing spawned a fully obnoxious kid (that became a decent adult in DS9). Then with Troi (WTF
) but Jadzia was the worst. At least in TNG it was contained to a few eps and then the show could go on.
Jadzia the Klingophile. I think it was just the constant fighting, so much soap opera that the writers felt that they had to spill it into Ezri at the end of s7.
Eh, DS9 was the most pairing focused show of the bunch unfortunately and it showed, because whatever problems Worf had with Jadzia, he would probably eventually have had with the more feminine Troi as well but TNG was smart enought to kick that premise in the nuts before it blossomed.
This pairing is different than say, Keiko and O'Brien, because Keiko never bought out the worst in O'Brien. Keiko was just a bad character, period. And Gul Dukat and Kai Winn were entertaining together.
2. Jadzia and Curzon.
It seems as time moved on, she became more and more Curzon. Maybe Sisko calling her Old Man all the time didn't help. She was so accomplished in her own right (multiple degrees) that it was really questionable what the symbiont added to her life besides some questionable obsessions.
Ezri really felt like a Jadzia 2.0 in some ways, and her struggles to break away from Jadzia's life was palpable. You really have to wonder how long symbionts live and after how many lifetimes they just start consuming their hosts altogether under the sheer weight of previous experiences.
It made me question the Trill obsession with symbionts isn't just some type of child abuse to farm children out to a leach type monster.