It's not unbeatable, they can only affect light not sound or scent. If you can use those two senses properly, you can counter them. It's not like they're moving any faster.
My input - it's less important that the ability itself is unique than it is whether you're capable of finding unique and creative ways to use it. Regarding this specific power, yes it's not a power I see very often and it does have potential to be used in a multitude of ways, but if the only way you show it being used is "They suckerpunched me, because I thought they over there, but they were really right in front of me," then it'll get stale. Not saying that's your only idea for it, but it's something you need to keep in mind, especially when it's not an inherently flashy or exciting power (for example, Dragon Ball gets a lot of mileage out of "shoots energy out of hands" because it's fun to watch no matter how often they do it).
For an analogy, there's an unofficial "creativity test" where you're given a normal brick and asked to list as many uses for it as possible. Lets say, instead, this is a character who has complete control over a single brick. Sounds boring, right? And it will be boring if the author only ever has them use the "bludgeon bad guy with a brick" technique. But what if they could ride the brick to fly? Or what if they can deconstruct the brick and reassemble it into different shapes? The more ways you can twist your mind to make this single, limited superpower work, the more likely your audience will want to tune in next time to see what crazy use you come up with next.
If anyone here is familiar with the Stands in Jojo's Bizarre Adventure, you can see how powers that seem very specific and constrained can produce a number of interesting scenarios you haven't considered before.
As for my last point, the name. I'd say "Light Manipulation" is too general, because there's a huge variety of things you can do with light. If this character can only manipulate light in this very specific manner (slowing it down as it enter's someone's eye) then a more specific name would be more appropriate. I'm not feeling especially creative right now, but "Light Slowing" or "Perception Slowing" would be more informative, though not very cool sounding.
To me it doesn't make much sense. How we process images has to do with how your brain functions, not how fast light goes. It would probably make more sense to give them psychic abilities that slows down the brain which makes it process slower.
If you want to deal with light manipulation, you could have your character go super fast that it leaves a ghosting effect similar to what happens during long exposure
This is one of those powers that can be brutal against unprepared opponents or people who are not good at adapting in combat.
Now, if the light manipulator is fighting against an opponent that guides themselves with their other senses either because they figured it out or because of their powers, that power is gonna be useless against them.
The heavy match up dependance can make the fight either an instant win or make the power useless, so i dont think it would be way too entertaining for a protagonist power.
Of course this is assuming that is the only use you are giving to the light manipulation.
There are many other ways to use literal light, like this one:
Working out that your opponent is causing a five second lag to your vision (which by the way would induce serious motion sickness in most people as your vision went out of sync with your movement) while in a frantic fight (and five seconds is a really long time in a fight, you could have easily just been stabbed or shot or punched out during that time) and closing your eyes to combat it, and not only that but then fighting blind would require the person to be incredibly smart, perceptive and quick thinking and also an incredible superhuman fighter. I haven't seen a lot of blind karate champions winning Olympic gold medals. If you were Daredevil with his superhuman senses that act like sonar and kind of allow him to "see", sure, but it's a better villain power exactly because you couldn't have every major antagonist the hero met have blind-fighting skills to stop him just running up and putting handcuffs on them before they even worked out what was happening or it'd get boring.
It's not a flexible power to build lots of interesting scenarios around. You can't rescue people from a burning building with it, or get across the city fast, or sense danger etc. It'd become a boring power in a narrative sense pretty quickly.
Makes sense to me - your brain processes images because light enters the eye. Manipulate the light and you manipulate what your brain sees. Same reason I see a dancer in your post but there's not a dancer actually in front of me, it's just light from my computer monitor.
This does provide more useful information for how this power can be used though. Does this person's power only slow down light or can it do other things to light? If it only slows, does it only slow down light as it's entering people's eyes? There are a number of implications that you can come to when you drill into how specifically your power works. Not saying it's better or worse to make the power more specific, but if you're the type of writer who can make it work, there's a lot to be gained from going down this line of thought.
I am not an expert in physics but I think that if you slow down light, it does not slow down processing or time, instead it just distorts the light. The ghosting in the image I posted is the result of manipulating time. So it would make more sense if the character moved super fast or if they could freeze time.
If the light reaching the person`s eye is slowed down, it would result in an interval where the person cant see because the light hasnt reached the eye in the first place. That doesnt slow down the perception of time. If you close your eyes, you can still count ten seconds accurately, for example.
Depending on how drastic and frequent are the changes of light, it could be the doom against oponents with epillepsia and it would be a real pain to rely on sight against said opponent.
I agree. Making the target's brain process light slower would be influencing the brain instead. Light manipulation would be distorting it (the light) as @NickRowler said.
Yeah maybe I should change it so that instead of slowing down light, it slows down the processing of the brain's visual cortex.
Right, you make a good point(NickRowler too). I admit, I was thinking in terms of my audience brain instead of my scientific brain - these sorts of explanations work if you just need to handwave an explanation for why a person can do what they do instead of just having it happen. But I'm a proponent of the idea that you don't need to be fully scientifically accurate in your explanations to create an engrossing story - you can always have some expository character say "In layman's terms, what they do is 'slow down' the light entering their eye, though scientifically that's not accurate at all' - as long as the science itself isn't the focus of the scene and you don't contradict your own established rules. I'm simplifying a whole theory of writing into a couple sentences, but hopefully it's clear enough so far.
My issue with responses like "Make it a psychic thing instead of a light thing" is that it feels like it's getting close to saying "just write a different thing." dongsunpai wasn't specific on what part of their idea they were most invested in, whether it was the nature of it being light based or just the perception altering aspect, but I'd say the crux of my advice is more "If you can come up with new and exciting ways to apply this ability to different circumstances, the ability itself doesn't necessarily matter."
If you want to stay with the concept of light, you could have them manipulating light to make an optical illusion.
@NickRowler That sounds epic for some odd reason…
How relevant is scientifical accuracy depends of the degree of realism of the story. While some stories make science step aside for the sake of "rule of cool", science can also be a tool to make a power way cooler. A solid example of this are all the clever aplications of alchemy on Full Metal Alchemist. Clever use of science in powers adds a strategic layer in combat that is really satisfying to watch.
Is truth that what matters is how the power is used, but depending on what you establish as the power makes some uses more or less beleivable.
It depends mostly of the uses granted to the power how much it changes things.
