6. Sito Jaxa Dies
Episode: Lower Decks (7.15)
A great follow-up to The First Duty, Sito Jaxa gets on the Enterprise because Picard requests her, trying to test her resolve after her being knocked down a couple pegs after the disciplinary action. She dies on an extremely important mission, and then Picard has to announce her death.
5. The Time Loop Begins
Episode: Cause & Effect (5.18)
Best opening teaser ever.
Death By Troggles 
Oh yes, these were both fantastic scenes! Lower Decks was one of the more interesting and moving season 7 episodes, and, yes, the teaser for Cause and Effect was jaw-dropping!
Yup, that teaser for “Cause and Effect” is fantastic. I loved that episode.