>>527774569
my prediction
>normal good ending
gaster or some other entity will explain very carefully how to fix the timeline once and for all. game will end with the roaring, but your battered body, surrounded by friends, hugging you as reality collapses as the titular "Don't Forget"-plays.
>true pacifist ending
prophecy is broken, everything is gay, okay all the way from here to L.A. and its happy ever after.
>snowgrave route
you die alone in the darkest dark, no one is there and you will spend your eternity in perpetual darkness... *You cried for help . . . *But nobody came.
>genocide
pretty much snowgrave's newgame+ the game then gives you the ability to go full genocide from ch1 and the game starts with susie never learning about kindness in ch1 and everything going worse from here, but this time there is no pretending anymore, no more happy friendship time.
this route would probably feature a lot of ralsei-bullying.