As with movies and other popular media, the ending of a project is just about the most important piece of the puzzle.
Without a solid closer, you'll leave audiences with a negative perception of the product which will likely cascade into other problems they found along the way. Stick the landing and send the fans home happy and you'll likely receive positive word of mouth, but if you stink up the place then even a 90% decent run could end in a skip fire.
And part of keeping the audience happy is most definitely by ending things on a positive note, to make them feel emotionally satisfied and look onwards to a brighter tomorrow. Therefore it's rather strange to find examples of devs who, for some reason or another, absolutely love making their downer or "bad" endings canon parts of the story. Characters remain dead, hope remains on the brink of being extinguished and ruined picnics seem to be the order of the day.
Cheery stuff right? Well at least for many examples on this list they lead to wild and wonderful sequels and successor franchises so maybe these were happy days in disguise!
8. Castlevania : Dawn Of Sorrow
So we start this list with a bit of a strange example, as technically both the "Bad" and the "Ultra Good" endings of Castlevania: Dawn Of Sorrow allows the player to unlock a brand new mode that carries on the story of our ill-fated protagonist Soma, however the fact that both points converge on this canon post-credits scene does strangely qualify for this list.
And if you don't like that justification just ask yourself this "are you really going to stop me from bringing more attention to this often overlooked area of the Castlevania franchise?"
So let's pick things up at the end of the game where, UH OH looks like you done made a whoopsie and forgot to equip a special amulet before fighting the final boss and now you're Dracula! Gosh, dangit! However, fret not my fanged friends because Julius Belmont is here to help with your situation in the brand new "Julius Mode" which sees you play through the entire game again with different a moveset and enemy placements with the goal of tearing your spirit from this mortal form.
Delicate he is not it seems.
Still what you do get is a rather heartfelt conclusion to the story, a wonderful new challenge, and an ending in which it's both good AND bad, which is just the sort of batshit experience you expect from a Castlevania game.