Neon Genesis: Evangelion: Shinji fails to recognize that life without suffering also makes life without love and the world remains a goopy mess. Alternatively, SEELE succeeds and makes themselves gods at the expense of the rest of humanity.
I thought Evangelion already had a bad ending(s), non-sensical as they already are.
Attack on Titan:
Eren isn’t stopped in the final arc and destroys the entire planet instead of just 80% of it.
Nightmare Before Christmas:
Jack dies when he’s shot out of the air. The houses he visited are terrified and people hurt or killed by the toys he left. Oogie kills Sally and Santa. Christmas no longer has a Santa and Oogie has more of a free hand to meddle not only with Halloweentown, but also the other holidays now that his goons know where the doors are.
Lord of the Rings:
The Battle for Middle Earth games pretty well summarized the worst case scenario there. Death, suffering, and slavery grip the entirety of the realm. The only being capable of stopping Sauron being Tom Bombadil if he bothered to care.
Tenacious D and the Pick of Destiny:
The D doesn’t play the best song in the world and Jack doesn’t block the lightning bolt from Satan. KG is sent to Hell to be a sex-slave, Jack dies, and the world falls to Satan.
James Bond:
Basically every movie except for the Craig films would result in at least one city going up in flames if not a full-blown WWIII. The Craig films kind of already have the shadow cabal largely in control of world events so they just solidify that and there’s more suffering in the world for the 99%.
Team America World Police:
Gary remains a drunk instead of trying to set things right. Kim Jong-Il isn’t stopped in his plan to launch an attack on the scale of 9/11 times 2,356; a plan so evil that nobody even knows how bad it is, except every country would be a third-world country.