In response to Chapter VII: Kid's Stuff, I received several comments as well as a handful of DMs inquiring about (L/N)'s power in comparison to the other characters in My Hero Academia. Rather than continue to answer every question individually, I figured it would be better to give an explanation.

The first few paragraphs of this chapter are a brief explanation of the thought process behind the story of Solstice and Eclipse. If you just want to know how powerful (L/N) is, skip to the bold headline.

The most commonly asked question I tend to receive is "Who could defeat (L/N) in a fight?"

First and foremost, it is important to remember what the focus of (L/N)'s story is, and in turn the story of Solstice and Eclipse. My Hero Academia is a story of good versus evil. There are good guys and there are bad guys. While Solstice and Eclipse certainly includes elements of this story, it really takes place in the moral grey area, and deals more with (L/N)'s internal conflict as he overcomes his own inner turmoil rather than the larger battle of heroes and villains.

I don't like drawing comparisons between (L/N) and other characters because the story is so different. For every character in My Hero Academia, the story is about them becoming stronger. Becoming more powerful so they can be better heroes. But from the very first chapter, (L/N) is already at 100% power. I made him that way for one main reason. To address the flaws I see with other My Hero fanfictions.

Typically, authors will create an absurdly overpowered main character because they think that that is going to make their story cool and make people want to read it. But when it comes down to it, the story lacks an actual story. Yes, stuff happens. But stuff happening does not make a story. There is no progression for their character because they don't understand how to write character development. And that's fine, because My Hero Academia doesn't have a lot of character development either. But the story is engaging because the characters have to overcome challenges. When you write a character that is overpowered, there is no challenge.

Additionally, because these authors do not understand character development, they don't really know how to develop a relationship between their character and the romantic interest. It just kind of happens out of nowhere. But real romance is built upon relationships. Why is Person A attracted to Person B and vis versa? And I don't mean just physical looks or common tropes of he's funny or charismatic. As I'm writing for Solstice and Eclipse, I'm asking myself, constantly, why does (L/N) need Yaoyorozu in his life and why does Yaoyorozu need (L/N)? What makes them unique to each other that would cause romantic feelings to arise? What struggles does their relationship face, and how do they overcome these struggles?

I wanted to hopefully demonstrate how to write an overpowered character correctly.

In short, Solstice and Eclipse is not a story about heroes and villains. Solstice and Eclipse is a story about every day people. It's about the human condition. It's the story about the inner battles every person faces told through the perspective of a lonely young man. (L/N)'s strength is not measured by how strong his quirk is, it's his internal strength that matters in this story, and how we see him grow as a person in that regard. How powerful he is, is irrelevant.

All this being said, let me answer your questions.

Who could defeat (L/N) in a fight?

First, consider there are several factors when answering this question. The most important one being (L/N)'s character. (L/N)'s entire story is one of someone who is afraid of hurting someone. This attitude would have a massive influence on the outcome of any and every fight he would get into. So, even if he is stronger than his opponent, he might lose simply because he is afraid of hurting them or someone else nearby.

So, let us first answer this question taking into consideration (L/N)'s fear of hurting people. This means he would only use his quirk in ways he is absolutely certain wouldn't result in him accidentally losing control and/or hurting someone. Well, he would still defeat most of the students at UA. His overwhelming power, even with the setback of his extreme trepidation and caution, simply outmatch most people. For instance, a simple wall would stop anything Oijiro or Kirishima could throw his way. They wouldn't be able to get through his defenses. But the more powerful, skilled, and intelligent characters would likely be able to defeat him. Following is a list of things that might allow someone to defeat (L/N), and an explanation to their meaning.

Reaction Speed: Is (L/N) fast enough to both notice, process, and then react to an opponent's attack? Can he respond quick enough to defend himself or evade?

Skill: What level of mastery does (L/N)'s opponent have over their quirk and how might this give them an edge?

Mobility: If (L/N) can react in time to an attack, can his opponent than maneuver around his defenses or reposition themselves quickly? Can they keep (L/N) in their range?

Power: Is the opponent strong enough to break through (L/N)'s defenses? Note that this also is effected by reaction time, as (L/N) needs more time to create stronger constructs. Or is their quirk uniquely situated to counter or avoid (L/N)'s quirk?

Intelligence/Combat Intuition: How quickly and effectively can (L/N)'s opponent identify his weaknesses and exploit them? How aware are they of their surroundings and their opponent?

With these things in consideration, I have compiled a list of characters who could defeat (L/N), listing the factors that would attribute to their victory. A character's name in italics means it is a toss up, as in they could either win or lose depending on how I chose to write it. These results are based on (L/N)'s current ability, and as Solstice and Eclipse progresses, things will change, and we'll explore that too.

Midorya: Reaction Speed, Mobility, Power, Intelligent/Combat Intuition

Bakugou: ALL OF THE ABOVE

Todoroki: ALL OF THE ABOVE

Iida: Reaction Speed, Mobility, Intelligence/Combat Intuition

Yaoyorozu: Skill, Power, Intelligence/Combat Intuition

Komori (1B): Power

Monoma: Power

Shinso: Power

Mirio: ALL OF THE ABOVE

Amajiki: Skill, Intelligence/Combat Intuition

Hado: Skill, Intelligence/Combat Intuition

All Might (Before Battle with AFO): ALL OF THE ABOVE

Endeavor: ALL OF THE ABOVE

Hawks: Reaction Speed, Mobility, Intelligence/Combat Intuition, Skill

Aizawa: ALL OF THE ABOVE

Thirteen: Power, Skill

Nezu: Power, Intelligence/Combat Intuition

Gang Orca: Power, Intelligence/Combat Intuition, Skill

Shigaraki: Power, Skill, Intelligence/Combat Intuition

All For One: ALL OF THE ABOVE

Toga: (Post Season 5) Power, Skill, Intelligence/Combat Intuition

Twice: Power (Post Season 5)

Muscular: Power, Intelligence/Combat Intuition

Machia: Power

These are most of the characters that could defeat (L/N) in a one on one fight. The villains would probably stand a better chance because they would be willing to endanger civilians to gain an upper hand. Now, once (L/N) has a better handle on his quirk, things will definitely change. Solstice and Eclipse will definitely see (L/N) have gained a greater level of mastery over his power come Season 6. So let's take a look at who could still pose a threat to him once we reach that point, and the conditions that may follow.

Midorya: His command of multiple quirks in combination of his greater level of control and higher potential power output could overpower (L/N).

Bakugou: Sheer skill and tenacity.

Todoroki: If he can land a hit on (L/N) before (L/N) can react, otherwise (L/N) would win.

Yaoyorozu: Solely because of her ability to create something that could reflect light.

All Might: Raw power

All For One: Multiple quirks and raw power

Thirteen: Because in my story, her quirk neutralizes (L/N)'s

Mirio: Can phase through (L/N)'s light, and is so goddamn skilled with his quirk. Like, seriously. He's the GOAT.

Machia: Raw power

Aizawa: Neutralizing (L/N)'s quirk

Shinso: If, and only if (L/N) allows him to use his quirk.

Endeavor: Skill and greater experience

Hawks: Same as Endeavor

Gang Orca: Sonar attacks are (L/N)'s greatest weakness.

Shigaraki: Depends on if I decide he can disintegrate (L/N)'s hard light. Also, after his powerup in Season 6, definitely a threat.

So, as you can see a lot of names disappeared, and a lot changed to italics. Again, it's interesting to note how some people's quirks are more uniquely situated to deal with (L/N). Even after his power up in Season 6, Shigaraki would have less of a chance of defeating (L/N) than Lemillion, simply because Mirio's quirk is better situated to fight (L/N).

Now, if we assume that (L/N) is not being held back by any sort of concern for casualties. If he is simply being measured by his abilities and power, there are very few people who could contend with him. Aizawa is a given, because he can turn off (L/N)'s quirk. But if (L/N) is willing to kill Aizawa before he gets the chance, then (L/N) obviously wins. Same thing with Mirio. If Mirio were to make even the slightest error, he would be vaporized instantly.

At 100% power, only Midorya at 100%, All Might at 100%, and AFO at 100%, would stand much of a chance.

In terms of raw power, there is almost no one who can contend with (L/N). And that is really due to the physical properties of light. For instance, if All Might in his prime were to punch as hard as he could, and (L/N) were to punch as hard as he could, All Might's punch would cause more damage. However, All Might's maximum power is limited by the fact that his quirk is an enhancement type. The only damage done is that done by his initial attack. (L/N), on the other hand, has the potential for more destruction because light doesn't stop traveling. In the story, this is one of the limits on (L/N)'s character. So the comparison here is that All Might, Midorya (at full potential), and AFO could, by my estimations, destroy all of Japan in seconds, but (L/N) could destroy the entire planet if he so chose.

But, this is highly against (L/N)'s character. The greatest limit on his power is himself. And that is something that has been repeatedly illustrated throughout Solstice and Eclipse. Still though, (L/N) as a fully realized professional hero would be a force to be reckoned with. I am excited to write for Season 6 so I can illustrate how powerful he is, and I have plans to write a few chapters or a short story that takes place, say, ten years after he graduates UA so I can write what he would look like as a pro.

I hope that answers your questions!

Edit: Apparently it didn't answer all of them.
So, how powerful is (L/N)?
Let me put it like this. For everyone in the comments that likes to compare him to a nuke, he's more powerful than that.
I don't have the scientific knowledge to give an exact quantification of his power, but in my mind he is basically the human embodiment of a supernova.

For reference, a supernova has about 100 Septillion times the amount of energy of that of the most powerful nuclear weapon ever created.