The Sudden Downer Ending, in which Shepard dies. Joker shouting an echoing "COMMANDER!" from the Normandy as Shepard's corpse floats through space while "Put Your Head On My Shoulder" by Paul Anka plays makes it so much worse.
When Shepard catches Liara and Garrus getting intimate, Garrus struggles to come up with an explanation as EDI's voice can be heard saying that he actually cannot defeat furfags, causing him to shed a Single Tear. He then slips off the elevator into the waiting paws of the furries, causing Garrus to shout a Big "NO!".
