[Unpublished stories cannot be embedded]

Summary: Sunset Shimmer, Celestia’s ambitious pupil, had been obsessed with the magic mirror Celestia had shown her, but her mentor was constantly rejecting her questions about it, so she decided to seek the answers herself.
She entered the forbidden section of the castle library, planning on learning at the forbidden knowledge for herself.
However, before she could cross the line, she remembered what the mirror had shown her at the end and considered the risk she was putting on everything she had achieved so far.
Finally, she decided to abandon her search and remain at Celestia’s side, achieving her dreams and ambitions with her teachings.
However, not long after her decision, she noticed a distance between her and Celestia, and it only got worse when one day, Celestia announced she had taken a new student under her wing, one that is much more like what the princess wanted her to be.

Initial thoughts: Firstly, the summary. It's too long, and over complicated. The way I'd suggest fixing this is summarize your summary.
Summary: Sunset Shimmer was Celestia's prized pupil, but her obession with the mirror was causing Celestia to doubt her as a future leader. Seeking out forbidden knowledge against Celestia's wishes, Sunset Shimmer began to become absorbed by power, could Twilight and her friends be her only hope?
See? Much shorter. Onto the story itself. I feel like this is a "let's put insert character here" into the beginning of mlp, and while I do see the potential here, it's never fully realized. It comes off like Sunset solves problem A only for problem B to come up, almost like it's espiodiac in nature, which could work if executed well. The reason I believe this feels lack luster is really any character could be Sunset, there's nothing specific about her other than perhaps the Author wanting her to lead this tale that suits her for this role. Replace her with Apple Bloom. How much does the plot change? But on a more positive note, I did like how the story is told over espiodes rather than just a jumbled up mess. 6/10

What I liked: The structure of the story, the pacing felt just about right. Sunset's development arc, and how she is able to connect with Luna (Nightmare moon.)

What I didn't like: The way it's formatted was good, but it feels flat. Like there wasn't enough emotion behind it. Also why comedy? I feel like this is tacked on and not really does it serve a point to the story, so I'd remove it.

Grammar: I saw many small typos, and a clear misuse of certain words at time, and while I'm not expert here, I say this could use a through look over. 7/10

Characterization: Sunset Shimmer, Celestia and Twilight are the main focus characters and for what we get, I can get behind most of it. I do feel that Celestia is a bit rash in her judgements, and how fast she goes from Sunset to Twilight, rather than trying to truly show Sunset how to grow. It's overall pretty decent, just Celestia seemed a little ooc at times. 8/10

Story/Concept: I have seen this concept before, but never executed in this way, it's quite stark contrast to what we are used to seeing. It's pretty good and I enjoyed it. 8/10.

Final score and thoughts: Overall, if you like Sunset Shimmer stories you will probably enjoy this one, just know it has issues with grammar, and feels very much like a retelling of the show through Sunset's eyes. While it's not a bad thing at all, this may bother some readers that want fresh material. 7/10

Total: 8+6+8+8+7=37/50
7.4/10

To the author: Keep writing and providing us with awesome stories, I feel there is a lot of potential here, and I hope you found what I had to say helpful. Also.

*pats head*

7232468
Thank you for taking the time to read it, especially since it borders the limits you asked for submission.

As I did with a previous review, I will explain some things that are unclear.

The summary being overlong has been brought up before, so I will look into it, however, if the summary that you present is what you would replace it for, it misses the intention of the story.

The fix-fic thing has also been brought up, but as I hinted in the last chapter, it is intentional to sound that way.

It comes off like Sunset solves problem A only for problem B to come up

Here you both got the message and missed it. It's supposed to be frustrating to Sunset that she basically is solving every pony’s problems without getting anything other than hurt or ignored. The next chapter delves into the problem, and eventually the story will abandon the episodic canon.

Replace her with Apple Bloom. How much does the plot change?

You would miss Twilight's sisterly relationship and conflict of interests, since Twilight is getting everything that Sunset wants, and she doesn't want to hate her for it. And also, Celestia's raising of Sunset as a kind of surrogate daughter. Also, Sunset is a complete stranger to everything in the canon show, almost seeming that she doesn't belong.

What I didn't like: The way it's formatted was good, but it feels flat. Like there wasn't enough emotion behind it. Also, why comedy? I feel like this is tacked on and not really does it serve a point to the story, so I'd remove it.

Yes, this is sadly my own incompetence with the English language since I just started writing in English since the start of quarantine. Hopefully more practice will help get it better.
The comedy tag is more to show that the story has a more positive tone overall, and that it's not just sad and tragic all the way.

I do feel that Celestia is a bit rash in her judgements, and how fast she goes from Sunset to Twilight, rather than trying to truly show Sunset how to grow

There are reasons for this that are hinted but not explained, it will come with time. Honestly, I would give the story to do a new review once it reached the end of the first "season" of Sunset's story. I just wanted a more critical point of view of the start to see how the story is building up to.

To the author: Keep writing and providing us with awesome stories, I feel there is a lot of potential here, and I hope you found what I had to say helpful.

Everything helps, the most difficult part for me has been finding people that see the story from a more critical point of view, and this helps me understand what people see in the story when they read it and how they interpret it.
Luckily seems that most is just things that haven't come up yet.

I again thank you for taking the time to read it and hope to make it better in the next chapters.

OH, and before I forget.

*pats head*

Have a nice day.