i disagree with those defending sombra
as we do not know what discord and NMM
did before banishment and queen chrysalis actually successful infiltrated the royal family for an extended period of time and noone was wiser. sombra may have done something in his past but it was not expanded on and he really did borderline nothing when he came back
Sombra definitely did more then Nightmare Moon. He came about as close as Chrysalis, but Discord trumps him as a villain hands down. Chrysalis pulls ahead cause of her villain song and…pretty much only that. Poor Nightmare Moon is just out of the running though.