In season 5 finale The Cutie Re-Mark, there are different futures of Equestria, and all of them are dominated by past villains. It was all because Starlight Glimmer has interfered with the Sonic Rainboom. With no Rainboom, the Mane 6 never formed their cutie mark connection and never come together in Ponyville. There are different timelines and fates of the characters after messing with the past.
King Sombera's Future
It was an altered third season of the show. It started when the Crystal Empire return after a thousand years, and King Sombera who came back as well, regained control. Princess Cadance and Shining Armor were possibly defeated and imprisoned easily by the evil king without the Mane 6 helping and the crystal heart was never found. He began a successful conquest across Equestria by starting up a huge war. As for Twilight's friends, they along with other ponies are force to take part in this conflict.
Queen Chrysalis' Future
It was likely started during the season 2 finale, A Canterlot Wedding. During the wedding without Twilight and her friends, Chrysalis fully gains control of Shining Armor without the real Cadance being rescued to warn the ponies and saving her fiancée, defeated Princess Celestia and forever imprisoned, and see easily conquered Canterlot and began dominating all of Equestria. Since then, ponies because paranoid after seeing what happened which forced them into hiding and plan the resistance, but losing because of numbers. Pinkie Pie and Fluttershy are part of the resistance while Applejack, Rarity, and Rainbow Dash are possibly imprisoned since the ones we saw are changelings to find the camp.
Nightmare Moon's Future
Without the Mane 6 finding the elements, Nightmare Moon banished Celestia to the moon and turned Equestria into night forever. Rarity and Rainbow Dash worked with her as a servent and guard.
Possible Future: Trixie
Trixie became unstoppable with the Alicorn Amulet. Without Twilight using the Magic of Friendship to out smart her, Trixie easily took over Ponyville and soon all of Equestria by becoming an evil tyrant ruler. She was going to make the three princesses of Equestria to be here miserable servents or become her jesters to perform.
You all know the rest of the futures without the Mane 6, especially the one where it becomes a wasteland with no life likely because of the villains fighting for control or other ponies can't figure out there own problems. The possible futures could have happened if Starlight permanently alters time.
Please comment on what you think.