"Unity" - this is kind of DS9's Season 8 finale since the "World's of Deep Space Nine" stories do act as Season 9's opening stories.
I still say that if one insists on the artificial "season" model, Unity
is more like the big sweeps event 2/3 of the way through the season and Worlds of DS9
is the last block of episodes, with Olympus Descending
as the cliffhanger finale, the end of the first full year post-"What You Leave Behind."