BTW, here's my opinion of that fight rn (Feel free to go to the TL;DR if that's too long):
How can Danny win?
It’s not unusual for him to go “Invisible/Intangibility+Possession” wombo combo and you’ll be right to think he won’t try this but I’d say he can’t rely on this: Problem lies in how unpredictable Ryuko (and Senketsu) can be.
You can be intangible while she winds up for a Decapitation Mode, yes but you can’t hit Ryuko either so you must have a tangible body to attack her. Invisibility does work unless he’s cocky enough not to notice the stadium sized, Senketsu eye fly swatter going down on him like the Election Arc in the anime. Possession may be his best bet but Ryuko has two layers of mind protection: First is Senketsu who’s able to take control of his wearer, making them unable to move. Note that Senketsu does struggle when stopping Maiko from hitting Mako but this delay can be beneficial to the other layer of protection: Ryuko’s Intangible red streak which can DIY gets her out of Mind control like the time she grabbed life fibers out of her skull. That means with enough strength, she can grab Danny and yeets him out of her! Truth be told, it’s limited intangibility applied to life fibers but it’s the kind of stuff that will make him shit his pants. Ryuko is not immune to possessions but she has ways to remedy it, forcing him to think outside the box.
Trash talking on Ryuko is a double edged sword: One good witty remark and he’ll dance with her like a toreador dodging a bull BUT it can horribly backfire when she’ll charge headfirst into him, making sure her scissors goes straight into his throat.
The one thing he has to figure out very fast is how Life Fiber regeneration can be negated by attacking a part on both sides at the same time. Only then, can he truly work with his genius, his reactive evolution (and ecto blasts) to smack her down. He may go for a Hydra tactic aka cutting one limb off and freeze the wound shut so that Life fibers can’t stitch themselves back. This tactic becomes useless against Kisaragi.
His win conditions is to not only outlasts Ryuko stamina-wise but to figure out how to negate Life Fiber regeneration before she finds a way to hurt him on both forms.
How can Ryuko win?
Stats-wise, she’s a heavy physical hitter: Even with his busted stats, Danny is but Class K compared to Ryuko’s Class M. Plus, Kisaragi gives massive stats boosts able to even her odds
At first, you’d think “Ok she’s dead bc she can’t hit a ghost.” but I think she will stand her ground. She never fought ghosts, yes but she has been known to outsmart others despite her brash attitude. Plus, we’re talking about EOS/IF! Ryuko so the whole “blood loss timeout” and “Banshi” limits are out of the window. Reaching Kisaragi is a must as her Reactive Evolution combo’d with Low Multiversal Life Fiber absorption makes her a dangerous foe, even to Danny who have proven to throw hands with Clockwork Phantom and win.
Danny’s stamina is impressive (dude healed from a neck snap in Season 1) but Ryuko has been shown able to take some of the most gruesome attacks and survives like a champ thanks to her Life Fiber regeneration. A wave of ectoblasts piercing her body? That does hurt but Satsuki went harder than that. Pinned to a wall by of ice? Senketsu can Seijin Shippu their way out or even melt it away because of her body temperature as Kisaragi.
One thing to look out for is whether Danny gets his hand on a scissor blade. The weapon is known for changing colors depending on their user, that’s a canon thing in both the anime and the game. My guess is that the moment Danny has one of these, it will not only turns green but can be ecto-contaminated (something he’ll do to further add power). This can drastically change the tide. On one hand, he can now slash her life fibers and swordfights (Thanks V-man). On the other hand, he has to make sure Ryuko doesn’t retrieve them bc otherwise, she has free, DIY anti-ghost, scissors blades. Good luck timing your intangibility against a Dual Decapitation mode with ectoplasm you imbued yourself, dumbass! This scenario may also happen if Ryuko parries enough ecto-blasts like crazy with her signature weapons (Cutting tennis balls in milli seconds does that to someone)
Her win conditions is to not only outlasts Danny but to trick him into using his own powers against him, leaving him vulnerable to Ryuko’s finishing moves.
Overall outcome: It's a TIE/DRAW
It all comes down to three things: Stamina, Reactive Evolution and Counters.
If you were to ignore their universe-centric powers, both are crafty and instinctive powerhouses with quasi-immortal regeneration. Whether it’s Ryuko’s nigh instantaneous regen against Ragyo’s blows or Danny’s body manipulation/intangibility combo when dodging is proof of their superhuman stamina.
These two can adapt like none other! Danny is implied to be a genius and can easily copy one’s move by seeing it once. Ryuko is a gifted, resourceful fighting wiz able to create improvised plans on the fly and Senketsu’s fast evolution rate marries very well with it to the point it’s scary. Just because one has more intelligence doesn’t mean they won’t be bamboozled.
Counters speaks of how fast they bypass a problem. Both have shown time and time again how they outsmarted/outpowered/outsped anyone they got. Ryuko managed to trick Ira by letting herself attached to his whip in order to rip him from the inside using Seijin. Danny got to trick Vlad before putting the anti-ghost belt and even convinced ghosts animals (who mind you, hunted him down) to get the V-man.
TL;DL: It's a TIE because it’s whoever gets to out react-evolve the other and depends on factors such as finding out weaknesses (Danny and how to nullify Life Fibers'regeneration without scissors) or tricking others into actions that will bite them in the long run (Ryuko and how to win a free DIY Anti-ghost weapons from the ghost you want to beat)
BONUS QUESTIONS:
Can Danny sabotage her Life Fiber Absorption/ascension into Kisaragi?
I can see him try to stop her from reaching Kisaragi but I have no idea of how exactly he’ll proceed. His best bet is maybe the Ghostly wail bc that thing managed to harm Clockwork! Phantom who could affect timelines and IF’s Life Fiber Absorption gets LF from all dimensions and timelines. I don’t see him cutting all individual life fibers manually...
Can Ryuko block his Ghostly Wail and reflect it using Senketsu Mubyōshi?
The Ghostly Wail is an emotional-drive-drugged sonic attack able to deny regeneration on a multiversal level. Senketsu Mubyōshi is a barrier able to protect from attacks and cancel out sound waves before redirecting said waves at the sender. Granted, it’s the most batshit, insane idea someone could pull off but hear me out:
If Ryuko manages to pull this by syncing Senketsu’s vibrations with her heartbeat before Danny winds up, this can be the Decisive blow as it become a stamina/willpower tug-o-war between the two.
If Ryuko and Senketsu fail, they’ll be blasted with a pure, emotionally-driven eldritch attack from the other side with no way to regenerate, Kisaragi or not (and straight into the Ghost Zone with her dad in the worst case scenario).
If Danny fails, he can be knocked into his human form right there by his own trump card (which is stronger than Dan’s, mind you), leaving him at the mercy of Ryuko, especially if she reached Kisaragi through the fight at some point.
There you go: That's my opinion on the matter if that helps. Also, it's my first post and holy moly: No wonder these two are my fave!