Who is he, and what's he done?
King Sombra is one of the recurring antagonists of the series, My Little Pony: Friendship is Magic. He is the main antagonist of the Season 3 two-part premiere "The Crystal Empire" and the Season 9 two-part premiere "The Beginning of the End". He is an evil tyrant and former ruler of the Crystal Empire one thousand years ago, until Princess Celestia and Princess Luna defeated him, turned him to shadow, and banished him into the ice of the forgotten north. Thousands of years later, the Empire and Sombra returned and he plans to reconquer the Empire so he can use his power to conquer all of Equestria with the help of his army of self-controlled Crystal Ponies. However, he was thwarted and defeated by Princess Cadance, Spike, and the Crystal Ponies use of the Crystal Heart.
In Season 9, King Sombra was resurrected by "Grogar" to join his team of villains so they can defeat Twilight and her friends and conquer Equestria. But Sombra refuses to join them and he sets out to conquer Equestria on his own, believing in full confidence that he is the most powerful creature in Equestria and that no one can defeat him again. Sombra succeeded in destroying the Tree and Elements of Harmony and has conquered both Ponyville and Canterlot. However, his overconfidence and ego are what led to his final defeat at the hooves of Twilight Sparkle and her friends.
King Sombra is arguably the darkest and evilest villain in My Little Pony: Friendship is Magic. He is known to be a Unicorn who's heart is as "black as night". Sombra does not show any compassion towards anyone and he refuses to ally with others, unlike the other villains in the series. Sombra is shown to be very sadistic as he appears to take delight in seeing others suffer. This is shown when Sombra uses his dark magic to show others their worst fears and he mind-controls his slaves to do his own bidding. He will even go as far as to enslave and corrupt children, such as Flurry Heart in the Season 9 premiere and when he corrupted a filly while conquering the Crystal Empire. Sombra even threatened to harm Flurry Heart unless Cadance and Shining Armor surrender to him, though this is only implied.
King Sombra enslaved the Crystal Ponies and ruled over the Empire one thousand years ago. Before he was defeated by Celestia and Luna, Sombra cast a spell on the Crystal Empire and the Crystal Ponies which causes the Kingdom to disappear into thin air for thousands of years. When the Empire returned, Sombra attempts to retake the Empire, while the ponies were cursed by Sombra to have amnesia. The Crystal Ponies fear King Sombra and his reign, as one of the Crystal Mares does not want to remember Sombra's reign. It is unknown if Sombra has ever punished his slaves for their disobedience, or if there has been any disobedience from his slaves at all. Sombra even refers to the Crystal Ponies as his "Crystal Slaves". Though it was not seen in the show, it is implied that Sombra may have also killed Queen Amore so he can take over the Empire.
Sombra is also shown to be very desperate when it comes to conquering Equestria, to the point that he will do whatever is necessary to get what he wants. For example, he chased Shining Armor and the Mane Six during their first encounter with him in his monstrous shadow form and he cursed Shining Armor's horn as black crystals grow on his horn and cut off his magic. He also appears to be laughing evilly when he sees Cadance losing all hope and struggling to use her magic to keep the barrier around the Empire so Sombra will not get in. Sombra was patient enough to wait until Cadance gives up and the barrier breaks. He was even gonna murder Spike when he attempts to take the Crystal Heart and regain his power. Luckily, Princess Cadance saved Spike and the Crystal Heart and Sombra was destroyed by the Crystal Heart.
In Season 9, Sombra becomes even more desperate than before, to the point he wasted no time to try and conquer Equestria after he was resurrected. He managed to destroy the Tree and Elements of Harmony and traps the Mane Six in his dark crystals. He was going to corrupt them but decided against it as he wants them to actually witness their own worst fears become a reality as he corrupts all of their friends and allies to do his bidding and they become his personal army to conquer Canterlot. During his final encounter with the Mane Six, Discord reveals that Fluttershy is his favorite, which causes Sombra to get a sadistic idea to attack and kill Fluttershy. Discord managed to save Fluttershy's life by blocking his magic and pretends to be harmed by Sombra.
King Sombra is also overconfident and has a huge ego. Sombra is pompous, self-centered, and arrogant as he believes that no one can stand in his way and that he is unbeatable. But when the Mane Six managed to overpower Sombra, his arrogance shatters and he breaks down, constantly trying to deny his upcoming defeat. Sombra managed to shoot one last magical blast against the Mane Six but fails. Because he is too irredeemable and cruel, Sombra was destroyed again and this time for good.
It is unknown why and how King Sombra became evil in the TV series, but he is shown to be a sadistic, cruel, and heartless villain with no redeemable qualities whatsoever. In the non-canonical IDW comics, that version of Sombra had a backstory and has redeemable qualities.
The TV Series version of Sombra hardly has any redeemable qualities. In the Season 9 premiere, Sombra briefly was honorable, as he stated he admired the fact that the Mane Six came to fight him with nothing but their wits, showing that he shows very small respect to the Mane Six for being worthy adversaries. However, this could also be false as he also called them foolish for thinking they have a chance against him and only said that he admired their courage mockingly instead of literally.
Other than that, King Sombra has no redeemable qualities whatsoever. However, in the IDW comics, that version of Sombra actually does have mitigating factors.
Difference between the Show and Comics
In the non-canonical IDW comics, Sombra appears to be more sympathetic and redeemable as he had a childhood friend, Radiant Hope. Unlike TV Sombra where he is willing to murder anyone who stands in his way, Comic Sombra is incapable to bring himself to kill Amore. Comic Sombra turns Amore to crystal and non-fatally shatters her instead. He also turned Celestia and Luna to stone instead of killing them and he still is shown to care for Radiant Hope, which led to his redemption. But again, this PE proposal is only for the canonical TV series version of him instead of the comics, so these do not count.
Despite Friendship is Magic's target demographic, the MLP franchise itself has had pure evil villains before, such as Tirac in G1 and Cosmos in the IDW comics. Due to all the atrocities, King Sombra has committed and the fact that he barely has any redeemable qualities whatsoever, I say it's a yes. Despite the fact that Sombra is overconfident and arrogant, that still doesn't reduce his chances of being pure evil; lots of villains like that were approved as pure evil. It should rather increase his chances of qualifying. What do you all think? Should King Sombra count as a purely evil villain or do you all think he is not qualified enough? Leave me your votes in the comments down below.