I was thinking that if Valiant can get a mention in this thread, then I'd 'like' to bring up Prodigal Daughter. I was getting a bit fed up with the Ezri overkill in the final season, and this episode in particular was one too far for me. I wasn't very invested in her family, and the mystery with the company and Norvo was dull. O'Brien shows up too late in the story, but when he does nothing interesting happens anyway.
I'm not sure why Ezri had to be anywhere near the follow-up to Honor Amongs Thieves in the first place, expecially as there was such a derth of O'Brien material that season.