Even when Discord was a villain I don’t think he was that evil. Lord Tirek assaulted crowds of ponies. stole their magic, and was a destructive, literally power-hungry, tyrant who’d of left Equestria a burning wasteland if he won.
Chrysalis was a war-mongering queen, whom tried to steal some other girl’s beloved, struck fear into her own subjects/children forcing them to be her army, (poor baby Thorax) and tried to conquer Equestria.
Sombra was a war-mongering king, whom enslaved an entire rare race of pony.
Discord was a cosmic troll, whom made it rain chocolate milk, made pigs fly, and make Big Mac think he is a dog. Say what you want about him, but I see no implication he was a mass-murderer like other villains, and such.
The fanbase’s fanfics, and such honestly exaggerated how villainous he was, he was almost nothing more then a comical nuisance like Q or Batmite, or Mr. Mxptlk.
Also, I don’t think he needs to of done a self-sacrifice, or be permanenty depowered, or turn into a normal pony, (ugh) to redeem himself, and that might be too much. He already risked his life/safety several times in the finale. It’s like you guys only notice his bad traits, and never any of his good. (In “What About Discord” despite it’s confusing nature was nice to see him get along with the mane characters, and I liked it when he befriended Spike & Mac. In the comics I liked it when he befriended the CMC too, shame that never happened in the show.)