There are four endings. Plus the Boston nuke one is literally a fucking meme that got so popular that Bethesda had to debunk it.
That meme has been around since nearly a month ago, how have you not heard of it?
BO3, dropkick your ****** edgy friends. "i dun wanna play BO3 itz 2 ezz for m333"
I hate all the kids that neglect to play titles like CoD and Battlefield just because they're mainstream and they don't consist of the four letters C, S, G and O.