Prototype & Alpha 1
The protagonist almost makes it into the basement in this version, but he is caught and buried alive by the Neighbor. Alpha 1's ending is mostly identical, but the basement door is unlocked, however the protagonist is once again caught and buried alive.
Note that the Pre-Alpha has no ending, as there is no basement.
The basement is developed in this version, the protagonist manages to enter and explore a bit of it before it ends on a scare chord. The Basement Trailer shows there would have been a whole section involving running from the Neighbor and escaping.
Instead of exploring the basement, a trigger sends the player to an ending where the house is brightly lit and the Neighbor is seen crying for unknown reasons. The game ends shortly afterwards.
Here, the double jump ability is required to explore much of the basement. The player must get to the door with a white glow inside it and overlayed by a shadow that vanishes upon approaching it. The ending shows the protagonist about to leave what seems to be his apartment, due to being evicted (judging by translation of the letter and in the E3 Beta Reveal).
HelloMods Secret Ending
In the modding competition "HelloMods" there are several unused ending maps. One of which, called "Final Thing" has the neighbor making child noises and playing with toy versions of his and the protagonist's cars. He walks over to a cupboard, knocks over a vase, and gets scared as the shadow appears in one of the windows. He climbs a staircase and the shadow breaks the house, the neighbor dies, and the level is reset. The player is supposed to block the shadow from killing the Neighbor, getting slightly bigger each time. After the player gets to the same size as the shadow, he is teleported to another ending, Final Battle Scene. This is where the shadow blows up, the neighbor waves goodbye to the player as the neighbor steps through the exit door. When the player walks through the door, he is teleported to an ending where he is in the intro house, and looking sadly at a painting in a closet where the basement should be. He walks down the street as the Alpha 2 intro music plays and the game ends.