The Quickening, DS9 4
Please don’t hear this and think me strange, but this episode is so good because lots of innocent people die. And our hero does a lot of failing.
Julian Bashir can not save victims of a Dominion-induced disease (The Blight) even with all his fancy Starfleet contraptions and high hopes. In the process, he learns a lot about himself.
There’s a third act switcheroo and some actually tense scenes. There’s also Michael Sarazin proving that, even in the mid-90s, when you want an actor as bad as Peter Fonda but can’t get him, there’s always Michael Sarazin.