10 Utterly Devastating Star Trek Endings That Came Out Of Nowhere
6. Crossfire
Odo's feelings for Kira had become increasingly obvious as time went on in Deep Space Nine, though it appeared that only Kira herself was ignorant of them. Crossfire sees Kira begin a relationship with Shakkar, her former resistance cell leader, and the current First Minister of Bajor.
The episode starts out in the form of a sweet, romantic tale. Odo has Kira's coffee ready and waiting for her in advance of their weekly meeting, while also ensuring that his spartan office is exactly the way he wants her to find it.
As her relationship with Shakkar grows, Odo's heart, such as it is, begins to break. It takes some tough love from Quark, of all people, to help him get to a point where he can deal with his feelings not being reciprocated. This episode is perhaps an outlier on this list as, rather than the ending being truly depressing, it is much more bittersweet. At this point in time, Odo loves Kira, but she doesn't love him back.
He leaves the bar at the end, seeing her with Shakkar, alone once more.