Okies, let's so about comparing Katsuo to Sagisō and how they would battle with Kiro.
In fact, first let me compare Sagisō and Kiro, specifically their Dojutsu. The reason for comparing their dojutsu is Katsuo's Water Shuriken Jutsu, which is almost a staple move. Not too much chakra, very versatile with lots of mobility. The Sharingan will have more troubles dealing with the Water Shuriken jutsu. If Kiro gets surrounded, the Sharingan can't help him against water shuriken he can't see, and considering his Sharingan is only 2-tomoe, it might not even help him against those he can see. The Sharingan can be overwhelmed by a high number of unpredictable objects moving at high speed, e.g. Killer Bee's Eight Swords.
That something Kiro would need to watch out for in a battle with Katsuo.
Now we can get back to a comparison of Katsuo vs Sagisō.
Katsuo especially outclasses Sagisō in all physical aspects, he's physically stronger, has a high base movement speed, carries higher fire-power, and his other stats are comparable, if only slightly worse than hers. E.g. defense, taijutsu, reaction speed, etc.
Offense
When we speak of physical strength and fire-power, it's a must that we discuss how each of the characters attacks. While everyone might argue about how LCM will protect Kiro from Sagisō's attack, throw that notion out the window for Katsuo cause LCM won't be helping you much. Sagisō's attacking potential mainly comes from the sharpness of her chakra and the precision with which she strikes. Katsuo applies his chakra to more direct, blunt strikes that slam opponents with pure force and kinetic energy. She's a surgical knife, while he's a sledgehammer, you do the math.
LCM might protect against piercing attacks (dubiously since it was Lightning vs Lightning, and regardless of what arguments you bring I highly doubt Wind-Chakra that can slice through boulders like butter can't cut through LCM especially when combined with the Gentle-Fist's ability to cut chakra, but I'll humor arguments against it for a while. No, the third Raikage isn't a standard that can be used to measure LCM because I 100% guarantee the 4th Raikage wasn't tanking a KCM-enhanced Rasenshuriken.) it definitely won't be protecting against blunt damage though.
Taijutsu
Katsuo, Sagisō, and Kiro are without a doubt the best Taijutsu users among our 16 and under Ocs. In terms of pure skill level, I'd call them all equal, however, when combat style is factored in I'd need to give the edge to Katsuo because based on my own fights against both, Katsuo has the better instinct or combat sense, at a level I would say is superior to my own.
Ninjutsu
This is a thing. Sagisō only possesses Wind Chakra while Kiro possesses [type]electric[/type] & [type]Fire[/type], but Katsuo possesses [type]water[/type] & [type]electric[/type], this is a very deciding factor because Water-Lightning does have more synergy than Lightning-Fire, and while lightning can block lightning, Kiro's Fire will lose to Katsuo's Water.
On a basic level, Katsuo has the advantage in Ninjutsu typage, but it really depends on utilization, which comes to a front with the next topic.
Defense
Imo, Katsuo can tank anything Kiro could throw at him. His chakra natures are good at suppressing Kiro's, he's got a combat style centered around defensively deflecting impacts, and while earth possessed the strongest defense, water is the more versatile defense. From impact to blunt force to lightning and fire, water can be used to deal or divert all of it.
Combat style
Zander's a slippery little Eel, he's got more tricks up his sleeve that I would expect from Retro. If the fight starts off anything like Sagisō's fight with Katsuo then Kiro might lose very miserably from losing his eyes early in the game. Sagisō has alternative methods of reacting even without her eyes, but we'll need to wait and see what retro comes up with.
Can't say too much on this topic though because styles adjust as needed, so new opponent, new approach.
TL;DR - Zander will snap Retro in half if he's not careful.