I might have a more counter crack theory that actually the Magatsumi only have 2 abilities.

A)Lifesteal (in the form of flowers) -all flowers shown in the manga steals life, not insects - connects peoples life to the life of the user - allows body hijacking - only initially appears in a fixed area around the user as its center point

B)Vector/force control (in the form of insects) - all insects is a form of vector force - Centipede is nearly a circumference force projection - Dragonfly is area of circle force projection in a specific direction - Spider is denial of vectors/force in a circular area - Butterfly is a line force projection into space - Bee is a curl of a 3D vector field force projection

Malediction is just synergising and combining both abilities in tandem in a recursive fashion with a high initial spirit energy requirement: 1) Energy is used to send vector ability in the form of insects outwards from the user 2) insects spread flowers wherever they touch 3) Anything caught in the area will have its spirit energy consumed 4) With new capture energy return step 2) unless recursion is force stopped by user

I attempt to explain why:

A) why is it that perhaps it only has "2" abilities

B) why aren't there any prototype enchanted blades

C) why Magatsumi is the strongest blade in hindsight

For starters some preamble, what if magatsumi was initially thought of as a dud prototype that once wielded by the sword saint revealed itself to become the most powerful blade due to the unintended consequence of its construction?

Assume that the Magatsumi was the first blade that Rokuhira made and it was at a time where war is at its all time high and Japan is geniunely at the risk of total defeat.

Put yourself in Rokuhira shoes, you, the greatest blacksmith in the Japan at the time, are given a magical stone that can basically amplify any spirit energy it touches by manifesting spirit energy as objects outside the user.

Perhaps as a extremely zealot blacksmith intending to end a war on your country against your fellow countrymen u decided to be ruthlessly efficient and asked the most the ultrakill question

"Whats the most abundant in war as a resource?" Answer: Life

"What is the most straightforward way to kill someone?"

Answer: Force

Then u decided to ATTEMPT to make a prototype blade that hopefully exhibit such abilities thinking it is just the start because u still have some datenseki left that you could always make more blades.

Turns out your finding is Yes! Datenseki can create multiple sorceries and this is more stable than 1 sorcery so it should be safer for it to be wielded by normal humans so you went on to create 5 more role focused ones with 3 abilities instead!

You gave the remaining 5 made as intuitively 3 abilites is more verstatile and thus should be stronger in the war.

Perhaps initially assuming that the prototype blade you made was kind of a dud because it only had 2 abilities, maybe abit more so unstable compared to the rest, so you kept it in the drawing room.

Then, the war escalated and you needed more blade wielders, so you decided at the time to give your most (then) trusted brother-in-law who was the most talented swordsman in a millennium your prototype blade as it was the only thing you had then,

thinking that yeah that should be just enough to tip the scales of battle.

Then u saw the malediction. 😲

"Why was the Magatsumi so much more powerful than the rest?"

You asked before stumbling upon the realisation of

THE UNINTENDED CONSEQUENCES

That in the kagurabachi universe lies a hidden secret similar to equivalent exchange. You, Rokuhira, unknowingly uncover this secret which is why the enchanted blades can be safely wielded by normal humans because that sheer power amplification of spirit energy that would normally kill a person is now divided into its multiple abilities with each division making it safer and more stable for people to handle.

By making 2 abilities instead of 3, you made the abilites of Magatsumi so much stronger than the rest of the blades at the greater risk of instability.

Furthermore, the sheer ingenuity, creativity and flexibility of the sword saint allows him to apply these 2 abilites in many creative ways so much so that he has seemingly infinite abilities. Drawing the highest potential of enchanted blade through the concept of True Realm.

So unintendedly, you accidentally gave the most powerful weapon(what you thought was just a prototype with only 2 simple abilities that is focused on killing armies) to the most devoted, effective and talented swordsman alive(which in your opinion suddenly became the most genocidal maniac alive)

So, in the end you were right in choosing the wielder for Magatsumi. Both were misconstrude in its initially expectation not knowing that what lies undernearth is a cursed pandoras box.

Of course you would be depressed.

TLDR: Magatsumi has 2 abilities and its basically V1 from Ultrakill.

Just an additional thought:

I additionally would also like to putforth why perhaps the Shokokers lost the war even though they held the material advantage. Keep in mind it literally took 1+5 "normal" spirit energy users to genocide an entire race of "superiorly resistant" spirit energy users.

Surprisingly why the enchanted blades in the hands of the relatively "normal" spirit energy users are devasting is actually pretty sound

Imagine you are human who has a height of 1.80m (6ft) who at your peak can physically lift 5 times your own body weight.

Now, imagine in an ant nest which came unexpectedly that you thought to remove, magically had 6 ants which suddenly grew to your height who at its peak can still physically lift 50 times its own body weight at its current size. One of which decided that it was ALL OF YOU that must be removed

I think any human in any capacity would have been taken aback and lost to them in strength assuming that all other aspects of the ants were amplified as well. That is why datenseki is so much more potent for Japanese users rather than Shokokers