Plot: There's intense, juicy buildup with Teddy and Henry's budding relationship, Cristina and Owen's fraying marriage, and Meredith and Derek's reconciliation. But the emotional peak of at the end of the season is an unexpected curveball with severe consequences. More on that below.
Ending: Devastating. Absolutely devastating, and happening for almost no rhyme or reason. A group of the surgeons (Meredith, Derek, Cristina, Arizona, Mark, and Lexie) take a plane to Boise to do a surgery to separate conjoined twins. But the plane crashes, leaving everyone hurt. Lexie eventually dies from her injuries, leaving Meredith and Mark in shambles.
Weepiness: There are pretty sad parts this season with Henry's death and Owen's affair, but none can beat the aforementioned.