You put Diamond and Silver in the same category as a griffin who threatened Fluttershy, An Elvis lookalike who purposely got ponies who work for him to fight amounst each other and set them as being worse then a Pegasus who almost got Twilight and her friends killed (then almost got Scootaloo killed) AND F***ING FLIM AND FLAM?!
 
ARE YOU OUT OF YOUR BUCKING MIND?!
 
Cozy Glow has no super powers, so despite her accomplishments she can’t be considered more than a villain.
 
Trixie was originally not more than an antagonist before she got the Alicorn Amulet that drove her mad with power. If anyone should be Somewhere In The Middle it should be Trixie.
 
All three of the In THE MIDDLE candidates actively harmed ponies, lied, cheated and stole. There’s nothing ambiguous about their actions. Both Flim and Flam and Lightning Dust returned to to do dastardly deeds. MAYBE Suri is in the middle only because we never saw her again after that one episode.

@Background Pony #CAEB
 
Like I said, you should switch some of the characters around since some of them did change for the better.

@Grogar  

 
Indeed! MLP’s answer to Thanos!
 

And I’m above them all.  
As the “Emperor of all Evil in Equestria!”

@JwwProd  
A villain is a kind of antagonist, but an antagonist is not always a villain.

@darknessRising24  
“Somewhere In The Middle” means worse than antagonists but not as bad as villains. In the middle.

@Background Pony #D1C9  
That’s the point. They’re worse than just antagonists, but they aren’t quite villains. They are, which is why I wrote it, “Somewhere In The Middle.”

I would switch “Antagonists” and “Somewhere In The Middle” around, at best Gilda, DT, and SS were just jerks and eventually turned over a new leaf, the ones in “Somewhere In The Middle” are still bad to an extent.

@JwwProd  
A Villain Protagonist and a Hero Antagonist.

@Cyan Lightning  

 
Death Note is also another good example of an Antagonist not being a villain. Like L is the main antagonist for most of the manga/anime but he is a good guy while the main character Light is a super villain.

Somewhere in the middle could ‘Rivals?’

@Background Pony #5FB1  
Accident.

Just a bit of information here.
 
Villain = A character whose evil actions or motives are important to the plot  
Antagonist = An antagonist is the character in a story that is against the protagonist
 
So antagonist may not a bad guy, like for example in GTA series for example, you can consider police as an antagonist due to protagonist role as a crime lord. And then we have Megamind movie, which basically the protagonist as supervillain. while the antagonist is a superhero.
 
So the better chart, I think would be just put “Villain” and “antagonist” in the same chart called “Villain”. Or just change the antagonist into “Mini villain”

@genervt  
What about the Wonderbolt Academy and the tornado?

@Background Pony #D1C9  
Dusty is just entertaining her fans with spectacular stunts.  
There is nothing antagonistic or psychopathic about that.

@Autumn_Shy  
F&F steal and lie, Suri also treats others like scum. Lightning Dust endanger fillies for petty reasons and cares not if her actions kill ponies as long as it furthers her goals, which looks a bit psychopathic, may I say.
 
They look pretty antagonist or worse for me.

@Background Pony #05FF  
I think OP meant those ponies are a “grey area” between good and bad ponies, thus they would be on the lesser end of the spectrum. (So to speak)

If there’s someone in the middle shouldn’t they be somewhat in the middle