I?m curious too, never saw the LS acronym before and when I looked it up I came up empty. I?m also curious why you are making your OC this powerful. I agree that you may need to make it a group battle at this rate.
Shinki would be high on my list of people to face this OC. She created her own world from scrach as well. And she would know best whether someone could be invincible in their own dimension or not, as well as the source of said persons invincibility.
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From here on I?m mostly responding to your OC as a challenge. Trying to beat him is a lot of fun, and I'll pull out all the stops:
With Flandre, I'm not sure making something simply into spirits would actually protect it from her. See, her ability is to, from any range, grab the 'eye' of anything, and crush it in her palm. Some might say that she crushes objects by crushing there spirit.
At this stage, a supreme version of Sakuya seems to be the best opponent for your OC. Manipulation of space and time that extends to whatever objects she chooses (as evidenced by the fact that the Scarlet Devil Mansion is bigger on the inside than the outside), and does so permanently. This all goes under the theory that Sakuya?s time based abilities ? placed to the max, exceed even the talents of Yukari. Ability to slow time to go with the ability to speed it up implemented onto the OC will let Yuuka do some very nasty things before he can respond. Or if Sakuya is alone, she could stop time, stab the OC repeatedly in the head, wait for him to be almost healed, and repeat; so that the character never gets an oportunity during which his brain works. A localized time stop may even last long enough for the full moon to come and Keine to rewriting history so that you character never discovers Gensokyo. In the mean time. Keine would probably be concealing a lot of history. However, even if she can't localize the time stop around the OC, the weapons the OC weilds have a good chance that their repair could be slowed and space manipulated much like the dimensions of the Scarlet Devil Mansion, or worse, the weapons copied much like Sakuya is thought to copy her knives.
Koishi Komeiji has complete manipulation of the subconscious. Her ability makes her the ultimate assassin, as it?s a type of psychic invisibility that lets her conceal anything, since she herself can steal your food without you realizing it. Utilizing her would probably protect the residents that aren't as good at combat, but are extremely effective at taking out threats indirectly. Or, since there's only one mind to deal with, she could even simply place Gensokyo into the OC's subconscious, thus protecting the country by removing it from the OC's mind.
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However, I think we can expand the ambiguous powers of touhou characters even more now that we have a Sue hardy enough to handle it.
A lot of touhou characters have a lot of abilities that are very ambiguous and get around the direct method. For example, Keine could hypothetically protect the world of Gensokyo from anything by rewriting the history of the thing if she can last until the full moon, so that the OC never encounters the universe. Remilia will most likely make sure Gensokyo?s fate is safe. Reimu interestingly has a spell card that lets her transcend reality, making her invincible.
From touhou wiki:
Fantasy Heaven
?Supreme Master-Arts by any means. With Reimu's ability to float, she floats from everything in reality and becomes invincible.
If it wasn't just for play (with time limit), no one could beat her with any method.?
The only way to beat it is timeout, but timeout is exclusive to spell cards and not to general battle, depending on interpretation.
Well, let me see, seems like the OC needs more specific detailed explanations on his abilities ( or maybe I could just give him more power-ups :derp:).
So yeah, Flandre has the ability to crush anything, and within your definition, she can crush spirits as well, yes? I don't think the OC needs a powerup up for this, I'll just assume the OC 'plays' with Flandre a bit, gets crushed and realizes that she's doing it with her hands and well, blow off her arm or put her hand into the Labyrinth Accelerator device and warp her hands elsewhere in Gensokyo/universe while locking her wrists to the Labyrinth Accelerator (while pulling another one out from the Labyrinth Accelerator). I assume that it takes time for the 'eye' of the object/thing to get into her hands so... yeah. It'll take time before Flandre can crush him again. (But you'll probably say, "Well, what if the 'eye' of the object can go through the time rift that the Labyrinth Accelerator created?", I'll just assume the 'eye' energy doesn't perceive time rifts very well and takes the long way home when going to her hands. I'll also assume that the 'eye' is as light as gas and travels at the same speed of gas as well)
For Keine well, the moon thing might work if they're still in Gensokyo, but at the ends of the universe, don't think so.
Sakuya seems like a good opponent too, but all that stabbing might just break the orb that's kept inside his head and literally cause the universe to die in an explosion equivalent to 12 alternate universes. Also I didn't specify where was the orb too and thus, I've decided it should be in the middle of the head (and, heeeereeee comes a little power boost :derp:), and that the orb will break into 12 smaller pieces (automatically if penetration/serious damaged has occured to the brain) and spread throughout his brain. The damaged caused by the spreading will be healed and the orbs become even more fragile to Sakuya's stabbing.
Koishi's trick of making my OC subconsciously deny Gensokyo can be easily dealt with by synchronizing with his former self's subconscious and his by taking anything he's forgotten (or subconsciously closed his eyes upon) back into his mind.
Reimu's spell card has an interesting flaw with it. If she transcends reality, does that mean she transcend into a higher plane of reality or just move onto a different plane of reality (that makes her invincble)? Because if it's the latter, my OC could easily deal with her on her plane of reality (this shouldn't be a problem since he can traverse multiverses and what not). If it's the former, well, my OC
might not be able to kill or hit her, but he can't die as well since he cannot die in any plane of reality.
Mokou can possess my character? Sure. Go ahead. If that happens, it's either the ghost calls in backup using the Labyrinth Accelerator and make the past/future selves synchronize with the posessed OC (thus making her obtaining their subconscious and obtain his powers as well). But as soon as they synchronize, two things might happen:
1) Mokou's mind will be broken as there are now 3 subconsciousness in her mind and they're all fighting over to whoever gets control of the body. Seeing as how Mokou is still human-like in thinking, this will make her turn retarded.
2) Mokou's posession will be expelled from the OC's body and thus making her power ineffective. (As a sadistic way of ending it, after Mokou has been expelled, the OC can summon two more of his selves and half-synchronize Mokou on each side. This will result in an incomplete synchronization and will end up with the body's immune system fighting off the other bodies' immune systems. Mokou will also have her mind broken (but not as badly as she's half-synchronized with the two) and she will become frail and weak. It's just like an immortal having AIDS and schizo at the same time! :derp:)
One question about Yuugi, does her power reaches to spiritual planes as well? If it doesn't, it instantly makes her a dead target.
Shinki should be praised highly as I see. But my OC has traveled in other universes and killed other Gods, of course, Shinki would be no problem to deal with, unless she has an amazing power that none of the Gods this OC has killed.