I didn't much care in the first place so I didn't bother, but since your offering, what are Sion's skill feats?
I'm glad that you (Or someone in general), finally asked! Give me some time, I will edit her feats into this post later.
Right, Sion. Before I explain why Sion is a absolute beast, I have to explain Knights first. Basically, in Knight Run Knights are elite soldiers tasked with infiltrating and assassinating High Level aliens, with the strongest being Zero Types. In order to be elected for the Knight order, one must be the cream of the crop across countless worlds. Only the most skilled and strongest are elected to become Knight Trainees. As a Trainee, you are trained in sword fighting and military tactics for years, until you can participate in the graduation exam, which is suriving on a real battlefield under Knight chaperons. This exams can be absolutely brutal though. We saw 1 such exam within the story, multiple transport ships full with trainees participated. Only 3 trainees survived that exam, even a Knight Chaperon died that day. So even if you are talented and special, you can still die like a dog on the battlefield.
Once you passed that, you become a Knight. Knights are supersoldiers who have to fight wars against flying, lasershooting aliens, with some high levels being able to whipe out entire military troops on their own, with nothing but a sword and the occasional, vanilla super power, like fire manipulation or telekinesis. Knights who have distinguished themselve on constant planetary wars can advance to Master Knight status, which are elites among elites. Master Knights are tasked with killing Zero Types, the strongest alien class out there. Zero Types can literally melt space fleets on their own and are unkillable without any Knight Support.
Lets talk about Zero Types more in depth. Zero Types are graded and range from D to SS. A single D rank could fight a group of 17 Knights plus 1 Master Knight, kill 5 Knights and hospitalize the other 12 and the Master Knight. The grades inbetween require a varying level of Master Knights. A S grade? They can stop multiple fleets plus armies of Master Knights on their own. Remember that.
Now back to the human side, lets talk about Cold Heroes and the Top Sword. Cold Heroes are legendary Knights that have been so powerful and skilled that they are frozen up and only thawed for when Humanity is on the brink of destruction. Cold Heroes are literal gods compared to your average Master Knight and only the top echelon is can become one. The Top Sword on the other hand, is the greatest Knight that currently lives. The Knight Order itself awards that title, making it objectivly correct in universe.
So much fluff that is basically just lolskillchain, now lets actually talk about Sion.
Technique copy: Sion can, with a single view on any martial art, perfectly copy the art. It was stated that Sion copies the art so well it becomes something she has done tens of thousands of time. Not only that, she can break the art done to its concept in her head. She could for example reconstruct a sword art whose theory was lost after witnissing it once, determine every stances' and moves' purpose and rebuild it into something personal.
Analytical Prediction: A somewhat weaker aspect of hers, but still pretty good. Sion can kick her sword high into the air in order to kill something high in the air and have it fall back into her hands while a enemy was speedamping towards. Said amp was described as being basically teleporation, and by reading it, she could perfecty counterattack it midteleportation.
Enhanced Senses: Sion scales above her pupil Clint, who learned everything from Sion. Clint could accuratly pinpoint an enemy through a multistory building full with other peoples, by tapping his sword onto the ground and feeling what he described as a "Dangerous step". Mofo could even tell their gender just by that.
Acrobatics: Every Knight worth their shit have to be able to fight in what Knight Run describes as "Spatial Combat". A Knight has to be able to fight to their fullest regardless of spatial allignment and footing, which echoes with the fact that Knights frequently have to engage in space battles.
Reflexes: Sion copied the Six Evil One God style and such as access to the First Evil, a pure reflex skill which allows for near unlimited counters.
Body Control: Sion can fight while her body is barely muscles on bones. Her entire body constantly breaking apart and rotting. Deathly sickly and radiated to hell and back and in spite of all of that can still fight.
AccelDev: The most skilled Knights where stated to be constantly evolving midfight against stronger enemies. Sion herself has done that to extraordinary degree and I will elaborate on that at a later section
Martial Arts/Sword mastery: Sion's sword art has been refined to the absolute limit. One of its signature characteristics is that the blade becomes invisible when she throws a cut. By freeing her sword of any form or rhythm, it becomes unperceiveable, something not achieveable by speed. Not only that, she possess numerous other Martial arts, including the Mayer Style, a ancient martial arts comprised of all earthly martial arts condenced into one Style, a Style so effective that it allows humans to fight with Aliens barehanded, the infamous Pray Style which is a far more powerful and effective form evolved from the Mayer Style and so on. Furthermore, Sion can reflect the physical force of attacks back at the attacker and neutralize attacks by using the same attack.
Now the most insane thing Sion did:
Sion Zail vs
Hyperion. Can't really explain why this is such a insane feat without explaining the fight, so bear with me.
To set the scene, prior to their final fight, Sion had a offscreen fight with Hyperion, there she was at peak condition. She barely evaded mutual destruction, but managed to kill Hyperion. Fast foward in their second and final fight, literally all odds are stacked against Sion. Before the fight even began, the condition of Sion could only be described as horrific. Girl was deathly sick, radiated to hell and back and had a barely functioning body. Her body looked worse than a slaughterhouse. If that sounded bad than wait till you hear the next thing. Even when she was healthy, Sion was the physically weaker one compared to Hyperion. Now get this, Hyperion passivly erodes space around it, cutting the physical stats of anyone standing inside said space by 80%. 80 PERCENT! To recap, Sion, who even at physical peak was weaker than her opponent, had to fight something in a near death state ON TOP of only having 20% of her strength left.
But wait, it gets worse. Hyperion possesses a Weapon called Mystletein, which has the pleasant ability of deconstructing everything it touches. A Single hit would be fatal for Sion. Additionally, Mysteltein can grant that ability to other spears, meaning that Hyperion could rain down oneshotting spears. Oh and its freely controlable, meaning that Hyperion could throw Mystletein, remote control it and have it return to it whenever and however it wants.
Ain't the end, Hyperion has 2 revives. Sion bested all of that above and killed Hyperion. Hyperion revived, got a powerup and hyperspeed movement. Sion killed it again. It revived ******* again. This time, it fused with Mystletein, amplyfing the deconstruction effect of it massivly. Just standing near it slowly eroded you and the range of that erosion aura was massive. So now Sion had kill Hyperion again, while it turned into General Grievous, got even stronger and slowly killed Sion by presence alone.
Sion finally killed it. And do you know what she had avaiable the entire fight? A Sword. With no hax attached to it. Sion fought Hyperion nonstop without any breaks throughout their fight, with nothing but a sword. Determination, Willpower and the duty to protect her homeworld and loved ones kept her going.
Not forgetting smaller fluff: Sion was a Top Sword and holds the second highest record of promotion speed with 2 years of Knight service before becoming the greatest Knight at that time. Hyperion was a Grade S Type Zero, Sion is the first and only Knight to have ever slain a Grade S alone and without any support. When Sion was a child, she whooped a seasoned Knights ass after 4 weeks of playtraining lol.