Tempest Shadow/Fizzlepop Berry Twist should be on this list. Not only was able to take out Celestia, Luna, Cadence in one fell swoop, but shows keen combat awareness both physical and magical. Plus was able to stalemate when the Storm King used the Staff of Sarcanas that contained nearly all the Alicorn magic. All with a broken unstable horn that in her book stated she trained to hone.

@Theponycaptorproject
 
white dwarf theory it is then.

@Background Pony #68FE  
As much as I love the idea that the sky is just a bowl, like in classical Greek mythology, Faust has confirmed otherwise.

@HDPlayer  
Their clouds seem to be semi-magical and don’t follow the exact laws of physics as we know them but are still in a sense clouds. They are small, can be stood on, carry a bit of weight, can be moved around and dispense a lot of water/lightning.  
There seem to be some binding forces at work that keep their clouds together and therefore a lot of water in one place. Pegasi are enough to produce a lot of those with moderate efford.
 
So a sun could be like those clouds. In fact, if alicorns were involved or simply a lot of unicorns they might even be able to create a sun or at least maintain it in a sense. It doesn’t seem that far off given their abilities.
 
Also some of what you said about the full planets worth of area. They only need the sun to work for a tiny area. That leaves the possibility that there might be more than one or it works differently in different places.
 
If we go by the technologically advanced scenario, the sun might be a fusion reactor in space. Think about it. It makes sense that we would want to power things in space and if we really got a fusion reactor there we could power it with just water for a long time. Maybe it is so advanced it maintains itself. The reactor could be like a giant lamp or there could just be a lamp.
 
Also things like the flim flams have shown us they can control or even power technology with their magic.
 
That being said the whole the sky is a screen theory would make sense too and explain a lot. Would be one heck of a revelation.

@Background Pony #68FE  
the fact that it would need to be either very dense to burn that long (or celstestia just feeds it hydrogen from somwhere every day), very cold compared to our sun and of course very tiny.
 
but i got 2 different theories/headcannons  
one of which is pretty much bullshit, but eh.
 

@HDPlayer  
But what if it’s just closer? I mean the sun is super far away, right? If it was as far away as the moon it would only have to be really small.  
Think about it. We are trying to harness nuclear fusion in reactors on earth. What stops her from moving a tiny magical sun in earths orbit?

@Theponycaptorproject  
celstial bodies* is the term
 
and well, true. but it is the closest we got. and star smaller than our sun wouldn’t be as warm and bright.

@HDPlayer  
To be fair, we don’t know if Equestria has equivalently sized heavenly bodies.

wait, Luna moves this compared to Celestia moving this.  
 
why is there such a small difference in their power?

@Background Pony #14FD  
How can she be stronger when she has left her studies and doesn’t even use magic?

@Background Pony #6B25  
She might just be able to liquefy mountains at that point.

Sunset Shimmer is stronger.

@Background Pony #FEDB  
Rarity is not stronger the Trixie, smarter yes stronger no.

I’m pretty sure Sunset is a tad bit more powerful than that.

This is base form only, right? We know that Twilight with the princesses’ powers in her, managed to match Tirek who had the magic of 95% of Equestria.
 
Also, Sunset’s “super form” can repair dimensionsal tears and overpower Midnight Sparkle in a beam struggle.
 
Starlight is a strange one. We never actually see her full power because she prefers using debuff magic and trickery, rather than straight up power struggle. Her “strength” seem to show up when everyone around her was weakened, debuffed or disabled.

Cadance should be a little higher. We often forget it was her magic alone protecting the entire Crystal Empire back in the season 3 premiere. Rarity also belongs on the chart above Trixie, we’ve seen her skills.

I think star swirl’s power should be lower than twi’s, otherwise pretty much spot on.

Season 1 Rarity is not on the scale and higher then Trixie so your scale is fake and gay.

You might want to tweak some of those numbers.

Discord wouldn’t even scale to this chart. When Faust created him, she literally compared him to a god.

@Spinny  
Remember in her first episode how Starlight had her attack easily blocked by Twilight. I don’t see her as stronger, just more creative.

@MadVillan  
People seem to forget that Celestia stopped NMM’s return more often than not in those alternate realities Starlight caused. For pretty much any of those realities to happen NMM had to have been stopped without the use of the elements at all, from that we can surmise that only reason she did use the elements was because that is the only non-lethal way of stopping her.

@MadVillan
 
Funny thing is, Luna knew Daybreaker’s name, without it being mentioned to her by anyone. Almost like she’s heard about it before somehow… not to mention the fact that she pretty much ignored Starlight in favor of Celestia, and seemed to have more insight into her thoughts than Starlight would realistically have. Who knows if Celestia was actually subconsciously projecting her own fears into the dream?
 
(Also, raw power isn’t everything, really)

@MadVillan  
Well… I was already REALLY biased, as I’ve never really liked Luna, and I’ve always found Celestia as the best princess, so you could blame that…