Magnus dying.

When Soren knocked Jesse unconscious while she was pretending to be an enderman. (scared the living cheese out of me.)

Sparklez death.

Dan and Lizzie's deaths.

Leaving Cassie Rose to die. (ok yeah, at least she has her cat with her for company, but we couldn't have left her a ladder?)

Gabriel basically dying, and then getting amnesia.

The witherstorm dying.

When Ivor made an iron golem that almost hit me in the face...twice, just saying.

Lukas or Petra blacking out after PAMA is destroyed. (imagine the strain on their minds ;-;.)

The witherstorm coming to Boomtown/Redstonia.

...

and REUBEN ;-;. :(.