Here is the full list of all 17 Last Year: The Nightmare achievements.
Be the first Survivor to finish a match in which all Survivors also finish the match.
Finish a match alive as a survivor.
Be the only survivor to finish a match alive.
Save a Survivor being grabbed by the Strangler by hitting him.
Abandon a trapped friend, and let them deal with the Killer alone...
Take out both a Killer and a fellow Survivor with a single Thermos Bomb.
As a Giant, throw a Survivor off of the top floor of the Belltower.
As a Killer, use an Execution move on a downed Survivor.
As a Killer, kill all the Survivors without more than 2 minutes between each kill, and without dying.
Go from one Survivor alive to having all Survivors alive in one game.
Kill yourself.
As a Killer, take out a full team of Survivors during the escape phase.
Spend 40 Scrap in a single match.
As a Killer, gas an unsuspecting survivor by rigging a Scavenge spot in Predator mode.
Barricade a trap door that you have previously fallen into during the same match.
Get killed by someone who already has this Achievement.
Put two Nail Gun Turrets next to each other and let them fight it out.