steven has them beat

@Mugen Kagemaru  
It’s from the S3 premiere, when Twilight trips down the long staircase in the castle.

Starlight used Reflega!
 
It’s a little TOO effective…
 
@Ihhh
 
Wait, what? Where’s that from?

@Mega PoNEO  
*fucking

Starlight and Twilight: We’re BUCKING invincible!

WTF BOOOM

@Background Pony #1566  
I would like to think Twilight taught Starlight pretty much all the spells she performed here with Starlight trying to impress Twilight by going above and beyond by trying to improve her shield spell and the others by combining the spells.
 
I would also like to think the spell she taught Twilight was cutie-mark related which Twilight has mentioned she isn’t too well-versed on (if that can still be taken at face value with the Meadowbrook retcon/“Twilight’s error”).
 
I sometimes wish power wasn’t a big deal to me. B-but it, but it does.

@Philweasel 
Well, up until Starlight blows it (literally), the fight was pretty well contained.

All I know is, you’d think Twilight would’ve equipped her castle with a shooting gallery rather than using the library.

Guys you gotta understand: Twilight’s teaching Starlight primarily in Friendship. The argument that “Twilight can do anything that Starlight can, because Twilight’s the teacher” is not going to work.
 
The relationship between Twilight and Starlight in terms of magical studies, is not of Mentor-Student, but of equal partners. Season 7 premiere implies that Starlight has mastered many spells and even taught Twilight other spells. This is the reason, in my opinion, why Twilight has a hard time letting her go.
 
There aren’t that many ponies who regularly challenges Twilight in magic, so probably Twilight finally feels less lonely in that department. I mean, there wasn’t really anyone else in her weight class. They’re either much lower or much higher.

…and kites.
 
Apparently that does enrich her life. Hey, I’m not gonna judge.

Twilight’s cutie mark is also not precisely the symbol of arcane might, but actually the symbol of friendship (is magic).
 
This is why Twilight is a beloved Princess with a castle, political power and dozens of friends, and Starlight is a emotional mess who has only been able to forge real connections with those almost as damaged as her.
 
This is My Little Pony. The ability to win in a fight is not the sole decider of worth. Starlight has never even been shown to be a particular good scientist or scholar. Where as Twilight has vast amounts of knowledge about all kinds of subjects, Starlight displays real knowledge of 1: Breaking people physiologically. 2: Mind control spells. 3: Destroying space/time.
 
None of these things enrich her life.

@Background Pony #61A2  
Twilight didn’t need wings to fly.  

@Philweasel 
Pretty much as you said.
 
/Nerd Mode On
 
It’s like the comparison between a wizard and a sorcerer from D&D.
 
Sorcerers have more “power” at their disposal over all, but wizards have access to a greater variety. Each is strong in it’s own right, and in the short term a sorcerer (Starlight) overtakes a wizard (Twilight), but in the long term, the wizard wins every time.
 
/Nerd Mode Off

Twilight is the choosen one pony to have magic itself as a cutie mark and ascended to become the alicorn of magic the very embodiment of magic itself but in this scene a random unicorn seems to cast more complex spells and also uses her magic to fly at the same time. I don’t see Glimmer’s cutie mark on the tree of harmony.  
Also flying with magic is really OP. Twilight had to get wings to fly and Starlight basically has wings.  
Now, I know this may be Twilight holding back so the full magnitude of her raw alicorn power is supposedly still greater than Starlight’s and she may also be able to fly faster but it’s crazy how potent Glimmer can be if the writers decide it.

Frankly it’s a sign of Starlight’s failings as a mage. As always she just throws around raw power without any thought to the consequence, where as Twilight actually pays attention to the purpose of the exercise.
 
…why they’re doing combat practice in the library I have no idea though…

@Xonxt 
Just asking, does a character have to blow something up every now and then to assure the audience he/she is still as powerful as ever?

@soundtea 
Yeah, but it’s been a while since Twilight did anything noteworthy with magic, so one starts to wonder…

@SunnySide 
There’s literally nothing that states Twilight can’t do this too. Especially since Twi’s the one teaching her.

@SunnySide 
Last time I checked Mary Sue is based on character not power level

“Not a mary sue!1”