everyone thinks that Sombra is a fail Villain
I Higly Doubt that
Basically, He’s the same as Sauron from Lord of the Rings
his presence is not dictated from what he’s doing, but from what he Did.
He’s been banished, turned into a shadow, a mere fraction of hate and evil that he was once. Wich was a being powerful enough to subjugate an empire, and that needed two princesses to stop him, and we’re talking about a Unicorn, not a demigod like the alicorns or a draconequus. Only the thought of him is enough to launch a civilization and their rulers into panic.
Sombra did his job well, wich was being the terrifying force that corrupts and destroy, the enemy force in the dualism of good and evil. No interpretations, nothing that leaves space to dramatization or similar, like Chrysalis, that did everything for her people, or Nightmare moon, wich was born from the need of being loved and from jealousy. Even Discord just accomplished his role as omnipresent spirit of Chaos.
King Sombra, in the end, was the First true villain of Friendship is magi.