If we want to expand this universe with many adventures for Twilight Sparkle and her friends from school then we need to think of a powerful villain that poses a serious threat to Twilight and her friends the same goes for her brother and parents not to mention the princesses. I was thinking on this villain could be an evil overlord of an empire or a disgraced knight that wanted to harness the power of an alicorn so he could achieve ultimate power.

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Imagine that Twilight's family have famkly rivals, even more so since Twilight is Celestia's favorite and Shnning is getting that lovey dovey princess of love.

Probably getting involved with an enemy that would love to get rid of them like getting in such creature like the Goblin king.

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A wise choice.

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And there could be some others who want them dead out of envy and lust for power. Just like how other bad guy ps are portrayed.

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I think that the nobles would have a beef against the Sparkle family and issued an old time duel from ages past Equestria; Capture the insignia.

I know, in know but we can't have dark themes here... well not that dark.

The nobles to ensure victory they snuck in goblins to have them through an accident for Twilight and friends.

All I can think of is a Gorilla called Monsoon. A traveling circus comes to Canterlot and the ringmaster, Stunning Stone, sets up a challenge to take the gorilla on in a wrestling match. Obvious cheating and scamming, Shinning Armour gets humiliated in front of town Ponies.

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And then the nobles are arrested for treason, aiding the Goblin King and for inflicting harm on Princess Celestia’s prized student and friends.

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Now that sounds genius for a story.

Another villain I was thinking on planning was a professor who believed that if he could create a world for his advanced technology to expand he could take over all of pony kind and then enslave them for his bidding.

Thought back on the Circus concept and thinks it should be a start off as separate from the Goblin king. Plus treason for laughing at Shinning is a bit much.
More likely with citizens and other guard ponies can't take Shinning seriously anymore. Causing him to become self-conscious and obsess over beating Monsoon. I like to think obsessive behavior runs in the family. With the ring master setting up the rematch to go for a draw. With this getting notice by Twi, or one of her friends, seeing Monsoon letting Shinning get some offense or the Stunning Stone Telling something to the Ref and said ref slow counting.
With the audience now behind the Underdog Shinning for the third match. Twi & co figure out that the whole thing was a set up to just make whole lotta money. With them planning the finish of the math based on the bets placed and stacking the deck against Shinning.
Maybe here we learn the reason Monsoon wrestle is because he has no money to retire. He been wrestling for long time and blown any earning long ago. Then Stunning tells him to go over to night. Maybe some kindness and help, Monsoon decide to let Shinning win. Allowing Shinning be taken seriously by once again. After the match Stunning would come in the Square Circle and berate Monsoon. After a Slap, Monsoon puts his hands on Stunnig's Ring Jacket and throw out of the Ring. He quit and is free from the Circus.
Couldn't really think of a ending, maybe gets a simple job behind a desk, or training other aspiring wrestlers. Maybe future appearances.

Another villain idea could be a sorceress that wants to harness unicorn magic. And an Orc warlock that has an army of his Orc warriors that want to conquer Equestria like the Goblin King. And the other could be the Lich, a powerful undead being that wants to extinguish all life both ponies and creatures.