@D  
Pretty sure NMM’s plan wouldn’t do so.  
She wanted her night to be loved/appreciated. It will be redundant if it ends up killing everyone, then no one would be able to love her night.  
She would clearly have to think that Eternal Night plan through. In fact the NMM timeline shown she figured something out since it looked like life managed normally despite it being night all the night and she stated its been years since she booted Celestia.

@Background Pony #D31E  
Problem is Celestia was sort of to blame too by not noticing Luna’s pain in time iirc.  
As in she didn’t notice Luna was suffering/having major issues and such before it was too late.
 
Really, I prefer they had it so Celestia says its her fault too for Luna’s fall to darkness rather than Luna alone is at fault. Just have the two say “We both screwed up bigtime”.

…  

you know.. I think that what you see is what pushes Celestia’s buttons all wrong, especially Discord, because she’s all into order and being a fair ruler, y’know?
 
plus, I tend think her maturity is above the irrelevancies of a small break up, or minor antagonism from someone specifically who is Trying to piss her off specifically, only because she seems quite mature. Maybe she isn’t all that much and I’m giving her too much credit, but I can’t see someone like Buddy here making her too mad anytime soon.
 

@Background Pony #613E  
Completely ignoring the fact Luna chose to accept dark power of evil within herself and knew exactly what she was doing and also apologized without prompting from Celestia.

The worst part wasn’t the banishment of her sister knowing she was possessed. Not even that she didn’t look for options. It was that she tried to make Luna (who was possessed at the time and therefore completely innocent) apologize for it and refused to take any blame herself.

1000 years in the sun.

@Background Pony #2F8F  
I don’t think their impermanence was up to her.

I think a thousand year sentence is a perfectly reasonable reaction to trying to kill everyone ever, and making their sentences not permanent is how you know she’s actually quite forgiving.

@Animed13253
 
It has the “tyrant Celestia” tag attached top it, so it’s kind of hard for me to lend a charitable interpretation to something that seems more like character bashing.
 
Granted I do agree Celestia is to contorted to easily lose her temper so if that ever happened, wow.

@D  
Still, none of said items would would really oiss Celestia off to no bounds. She was relatively calm when discord returned. He means what would happen when she got REALLY ANGRY. Heck, she put up a good fight against chrysalis (still losing though) barely trying! Look at Celestia’s face. She’s perfectly calm.

NMM’s plan would kill everything on the planet.  
Discord tortured ponies and had to be magically bound to fluttershy after 1000 year in prison before learning anything.  
Luna helped seal Sombra and it was explained what he did, he enslaved an empire and tortured the ponies.

@Kanrabat  
Yeah taking you place on top of the Heap over the dead carcases of your Enemies could do that to ya….

Chrysalis tries to feed her people by killing everyone in Canterlot. Hit by a force field directly landing in a town of lovey dovey animals during a fucking LOVE PARADE! Then they do the meanest thing of all after her second attack. Lock her in her own castle and have pinkie pie voice singing the song that never ends until they find a word that rhymes with orange…. Or a thousand years….

@Kanrabat  
I see where you’re going, after 1000 years, ponies still fear her and are worried that she’ll send them to the moon.
 
Celestia: Oh for Faust’s sake, I’ve changed over 1000 years, can’t we just move on?!

Ok, let’s not speak about the first two, because those arguments are stupid too, but Sombra?! He enslaved a whole nation, for Pete’s sake!

In my head canon, Celestia was a very young and immature ruler 1000 years ago. She had a very shot fuse and was the infamous “Tyranestia” everypiny feared.
 
However, 1000 years IS a pretty long time and as she matured, she mellowed-out and became to benevolent ruler she is today.

The first one nearly threw Equestria in an Ice age that would have killed a lot of ponies, and assuming there were survivors, they would be forced into worshiping a tyrant.  
The second one wasn’t exactly open to conversation when he was out there, having the time of his fucking life turning the lives of millions into pure fucking misery.  
And the third one had possession of an artifact that, if used for evil, would spell doom for the entirety of Equestria.
 
So, yeah, not feeling it, jackass.

@Star Cavalcade
 
Someone she has a chance of beating…
 
Maybe if she hires a new army, her old one flopped in like 15 seconds flat.

Seem legit

The whole “eternal night, leaving the planet a frozen wasteland.” “Screwing with the minds and souls of everyone” and “slavery” might also might have something to do with all that.

She doesn’t want to kill. We can only assume she wasn’t going to kill Chrysalis, just turn her into stone or something.
 
Of course, there seems to be some weird 1000-year limit on her magic.

Man, Sombrero got a raw deal, having to fight Cadence and all that. Celestia will give anybody a second chance, but her? Princess of Love will friggin kill your ass!

Oh great, more tyrant Celestia.
 
The only thing that bothered me is that she wished to regenerate Discord only to use his powers, not because it’s best than keep him trapped forever.

@The Floor Kippers  
Let’s just settle with “a long time ago”, ok?