@Background Pony #2BB5
 
Season 9, especially it’s latter half, was written with the “Show’s ending, wrap it up” Mindset.  
The last half of the season, 90% of the episodes were either rudimentary or downright awful.  
The Series Finale is actually one of the lesser evils of Season 9. The Season Finale was far worse.  
No one was ever going to get exactly what they wanted because the directors no longer cared.  
Also, kid villains suck. I have always had this thought. She should have never been introduced in the first place. Even when I myself was a kid I thought kid villains were stupid, with the only exception being Codename: Kids Next Door, but that’s because that was mixed with kid and adult villains from the beginning, and not what FIM did and randomly went “Oh here’s a kid villain all of a sudden.”
 
Cozy Glow is an awful character, that had so many other established characters rewritten just so she could benefit/beat them it’s not even funny. The Season 8 Finale was garbage. Starlight literally being forced to forget that she herself was a master of manipulation was so stupid. Especially since she clearly understood Cozy liked manipulating others earlier in the season. What Beau said at one point rings true, the Season 9 Finale would have been better without Cozy Glow. I have different reasons for saying that, but it really would have. I’m also in the minority in that the only villain of that trio I really cared about was Tirek. Chrysalis is overrated and her biggest power is her biggest weakness, I’m not really a fan of that trope. Especially when it’s one as mundane and overplayed as “The Power of Love.” She lost in the Season 2 Finale and Season 6 Finale for the same reason. “Give me all your love! Oh wait… no no NO NO NOT THAT MUCH THAT’S TOO MUCH!” I don’t care what anyone says, that’s a Deus Ex Machina when the only way you can defeat the villain is by exposing them to “too much” of their biggest strength. When you have to Deus Ex Machina the same villain twice, I think it kind of hints the villain’s not actually a very good one. Chrysalis had an interesting concept, but a very poor execution.
 
Tirek on the other hand, while he is mainly a powerhouse, that is not the only thing he is, as some people seem to think. He’s always been very smart. Both in the Season 4 finale, and throughout Season 9. I wish we could have seen some more of his articulate side. It was basically one smart villain and two complete idiots. An old, but wise villain, a literal child, and a psychopath.
 
I will agree that since she DOES exist, she was worth saving just as Discord was. What really irked me about that moment is that the reason they all got statued was because of Chrysalis. Everyone saying none of them wanted to reform should really rewatch the ending. Tirek and Cozy were downright TERRIFIED. They realized that at this point, there was truly no way they could ever defeat the Land of Equestria, and that it was probably time to change their ways. But then Chrysalis in all of her psychopathic idiocy decided to scream at the top of her lungs “WE WILL ALWAYS COME BACK! WE WILL NEVER BE DEFEATED!” without even giving Tirek or Cozy a chance to talk for themselves. It lead to them getting cupcaked by Chaos Pinkie, and then stoned before Tirek or Cozy had a chance to defend themselves.
 
I believe Cozy and even Tirek could have been reformed.  
Chrysalis was the only lost cause, and the only one who should have been stoned.  
She was never going to change because she was literally mindless. She was a rabid animal at that point.

@Scp-3125  
She’s just as worth saving as Discord, if not more.

@Background Pony #2BB5  
Whatever she is she probably isn’t worth saving

@Scp-3125  
There is no proof that she has that condition. We simply don’t have enough knowladge to make such a claim.

@dragon ball fan qooo  
Yes, but she’s been rehabilitated since she was a sociopath, and not a psychopath like Cozy glow

@Scp-3125  
Cough StarlightNearlyDestroyedTheSpace-TimeContinuumForPettyRevenge Cough

Cozy Glow Get Punish Is Right Way To Do It

you may be nine, but age is just a number!

And you nearly caused the apocalypse

@Background Pony #94BA  
OH MY GOD…it was her destiny

Nine…the same number of Circles Of Hell!
 
And guess what the ninth circle is.
 
Treachery!
 
Exactly what Cozy is guilty of.

So young and so rotten.

@Beau Skunky  
Sombra got the short end of the stick…killed…brought back…rekilled. Like honestly that’s probably amongst the worst things discord caused (in the final season…he did rule the world in perpetual chaos for a while) remorselessly

@Mildgyth  
the comment bell motified me of your comment… after I just read it… this is weird.

@Background Human  
I blame the Nobility for that, making Equestria into an Isolationist State following Lunas’ 1000 year banishment and Celestia moving the Seat of Power from the Everfree to Canterlot. It was only a matter of time and patience that Equestria was slowly on its way to the days of The Three Tribes before the founding of Equestria.

@Mildgyth  
Equestria has never been very good at following up on banishment.

@asdtroi
 
This is par of course, though. If there was any kind of regular check, Tirek’s first escape would have been noticed much earlier.

@Background Pony #187F  
We don’t even know the significance of the Skull, let alone any concise backstory to her character to justify the actions she has taken. All that most of us sees is that Cozy Glow was wrongfully tried in this to be sentenced to Tartarus no questions asked. Then to be sentenced to eternal petrification for a crime that DISCORD caused to happen.

@Beau Skunky  
Still, a simple chewing out is nothing compared to being petrified, and a frankly Discord was also in charge of his own actions in encouraging the trio. (I know, but I find them to be good arguments, plus I’m not very good at debating if I’m being honest).
 
The way they ended up helping each other, butting heads, the campfire scene and the way they almost had a revelation near the end were such good moments for them.
 
Speaking of that moment near the end, it still happened and the fact that they had to be snapped out of it shows to me and many others that there is still hope for them.
 
As for Tirek, while I wasn’t talking about him specifically I wouldn’t have minded seeing him reformed even in s5 after seeing his prison, although I will say that he wasn’t as a “priority” as Cozy.
 
I think fans were complaining about how he was reformed as opposed to being reformed. Looking back, I am also angry at how Discord practically sent that guy to his second “death” right after reviving him. Its just a shame we didn’t get more of him.

@northern haste  
Sometimes I wish that were canon. lol

Lies you’re clearly just a midget

@Background Pony #2BB5  
Yeah, but they’re still in charge of their own actions, and I recall Celestia chewed out Discord, so he wasn’t quite easily forgiven.  
(No offense, but it seems you tend to repeat alot of things alot of people whom argue about this say.)
 
I don’t think they were meant to be “likeable” in “Frenemies,” (only about as much as villains can be) as they still had evil intentions in it, and still didn’t like each other.  
That bit at the end where they “almost” learn a lesson in friendship, (only to shrug it off disgisted at the idea) just seemed like a joke on the show’s usual “touching lesson of the day” aspect, and I don’t think that was meant to show they’re somehow “goid deep down,” (in fact, they still kinda hated each other despite teaming up) I don’t quite understand why you guys take an obvious joke like that so literally, or constantly use that in these “villainous trio/finale” debates.
 
I honestly can’t see a character like Tirek suddenly making nice, and having tea & cakes with ponies. In fact, honestly before the finale, I never saw anybody care about reforming him, and people only suddenly have sympathy for him, because of their sympathy/fondness for Cozy, and/or Chrysalis. (Or because they didn’t like how the show ended.)  
Meanwhile, I hardly see anyone argue for Sombra, and he arguably suffered a worse fate. (In fact, fans got angry when the IDW comic canon tried to make Sombra more sympathetic.)

@Beau Skunky  
Considering that the villianous trio’s actions were partially his doing (gave them the means, brought them together encouraged them) and the fact that he was still using others like pawns and the trio’s own punishment (plus Sombra if you count him), he got off really lightly and was almost instantly forgiven.
 
Discord didn’t show any positive traits prior to his reformation. And with Tirek, he only showed a bit of regret when the Main 6 were being drained and even then, he only betrayed him after he himself got drained. Cozy at least had that small moment near the end of Frenemies and a tiny bit of leeway due to her being a child as opposed to an ancient lord of chaos.
 
Its not just that Grogar wasn’t around, its that they made the trio so damn likable in their episode only to do a complete 180 and make them look as evil as possible. They had such a great setup for possibly the best reformation in the series and it was completely wasted. Grogar could have also been built up throughout the season to make him suitably good as a final villain if he would still be a thing. As it is now I can’t help but see it as a disservice to both Discord and the trio (and possibly Sombra).

@Background Pony #2BB5  
He did get punished, seeing as he wasn’t just depowered “for a few hours,” he had to make a huge tiring journey on foot all the way back to Equestria, (and a being like him whom could usually go anywhere he wants with his magic probably isn’t used to that) and he did get imprisoned by the villainous trio, and at one point Tirek tried to kill him. But he did try to make up for it when he tried to help Celestia & Luna fight them off, and let the Mane 6 escape, even when he was depowered risking his own life.  
The problem with Cozy, and the others are she never showed any positive traits, and it seems like the staff never had any intention to redeem her. Even that one time Discord worked with Tirek there were brief moments he looked like he regretted what he was doing even before Tirek betrayed him. So I dunno.
 
At first, I was a li’l disapointed about Groger, (especially, sense he was a classic G1 villain) but I guess looking back, Groger probably would’ve just been a generic “doomsday villain,” or “Thanos,” while the villainous trio are more liked by the fanbase, so it’s understandable why they gave them top billing instead of a new “big bad” coming out of nowhere, and their successfull betrayal was probably less predictable.