Itsuki's strength as off Chapter 60

Itsuki's strength of chapter 60 (End of Volume2)

Hakuda Master:

Being a former corps commander of the detention unit, he has an exceedingly high mastery of Hakuda. Upon having his zanpakutos absorb vasto lorde level hollow powers, he has increased reaction times, higher physical strength and tough skin making him unparalleled throughout Soul Society. If we look at technique, then people like Urahara Kisuke, the former captain of the detention unit, Shihouin Yoruichi, Genryusai Yamamoto, all have a higher mastery. But in a true fight against Yoruichi and Urahara, Itsuki would win. He has learnt Shunko from Yoruichi. As for Yamamoto, he has better skill and strength so it will be a difficult fight.

Kido Master:

Although Itsuki doesn't pay attention to Kido he still trains in it. The only person that has a higher kido mastery than him is Aizen, Tsukabishi Tessai, the former captain of the Kido corps and Yamamoto. Urahara Kisuke could be on par with him. Yamamoto has a higher mastery than even Aizen.

Shunpo Master:

Itsuki's fighting ability is based off speed and strength, with speed being the main foundation. Upon having his zanpakutos absorb vasto lorde level hollow powers, he has access to the base abilities of an arrancar. This means including Sonido. After a period of training, Itsuki was able to combine Sonido with Shunpo reaching new heights in speed reaching on par with Yamamotos.

Master Swordsmen:

Itsuki is recognised by the skills of his sword. After transcending Hiten mitsurugi-ryu, Itsuki has created his own sword technique whose speed, even Yamamoto would find difficult to grasp. Out of all the techniques of a Shinigami, Swordsmanship is what Itsuki is best at. He has also created a Shunko to use with his swords. Only Yamamoto can give Itsuki a good fight in pure swordsmanship

It's simple to say that apart from Yamamoto no one in the three realms can best Itsuki in Speed and Swordsmanship.

Reiryoku/Reiatsu:

Itsuki's Reiatsu is off the charts. Before absorbing the hollow, it had reached immense levels and was only a bit higher than Zaraki kenpachi's. In recent chapters it was stated to be at advance-captain levels. After absorbing the hollow, his reiatsu has increased to new heights, as it can pressurise the whole of Seireitei. With this, one can tell that Itsuki's reiatsu has almost reached Yamamoto's.

Mental capabilities:

Itsuki's mental capabilities have increased upon the absorption of the vasto lorde level hollow. Although it would be shown in later chapters, His memory partition and thoughts acceleration had doubled into having 10 partitions and a 1200% boost in thoughts acceleration

His mystic eyes have also upgraded to being able to cut through the concept of space. Due to it being weak as well, Itsuki is unable to kill it but he knows he is increasingly closer to it. As for Illusions (Kyoka Suigetsu) Itsuki doesn't know.

Using the method of loci, Itsuki has memorised the whole Daireishokairo, the great spirit library that hosts all the knowledge of Soul Society.

Zanpakuto:

Ryurai – A lightning zanpakuto

Call out = "Reign from above Ryurai

Ryurai has the ability to wield lightning and empower the Itsuki with it, once more increasing his speed. Every move Itsuki makes is as fast as lightning while the blade looks like lightning from a distance. In its sealed form, Ryurai's butt at its hilt has a mirror like object where, upon feeding it reiatsu, can cause a flash of light, blinding anyone within a certain radius.

Byakko – A wind zanpakuto

Call out = "Shred to pieces, Byakko"

Byakko is a more passive zanpakuto focusing on defence. Although it is able to empower Itsuki with its wind, increasing his speed, it has no attacking capability. The wind has a special property of nullifying reiatsu. So, things like attacks, barriers and the lot that use reishi as to power itself is completely useless in front of it. In its sealed form, Byakko has a special property of not making any noise when the blade is swung. Every blade makes some sort of noise when it's swung, like cutting through air, but Byakko doesn't have it. It has no Physical defence capability.

Shikai:

Before absorption of Hollow – After calling out the names of each sword, blue and grey gauntlets appear on his hands. The grey one wields Byakko while the blue one wields Ryurai. Byakko is missing a metallic blade as it is now a blade made of the special nullifying wind with green lines flashing here and there while Ryurai has lightning streaking across it.

After absorption of hollow – Unknown

Bankai – Call out "Bankai, Susanoo":

Before absorption of hollow – When Itsuki unleashes Bankai, a suit of black samurai appears with a flag extending out of his back that depicts a dragon and tiger roaring at each other. This suit of armour is Byakko. Ryurai, however, turns into a two-meter long Odachi. Itsuki's speed is once again amplified while the area surrounding him is in chaos. A storm gathers while tornadoes and flashes of lightning surround him. The area surrounding him becomes a no zone for reishi powered attack as it nullifies them.

Ultimate form: "Kumano Ketsumiko no Kami, Susanoo!" Although the ability wasn't properly shown, it had been implied that Itsuki found it difficult to control. What we do know is that his Odachi becomes a two-sided sword and his powers have a tremendous increase.

After absorption of hollow – Unknown

Techniques:

Unknown Hakuda technique

All kido spells

Unknows Shunpo technique (Mixture of Shunpo and Sonido)

Unknown Swordsman technique

Hiten mitsurugi-ryu

Shunko

Ikkotsu and Sokotsu (Yamamoto's Hakuda technique)

Cero

Descorrer (Technique to open a Garganta)

High-Speed Regeneration (Still need to find Itsuki's limits)

Pesquisa (Technique to locate Reiatsu)

Overall strength:

It has been implied that Itsuki can give a good fight to Yamamoto without using his shikai before absorbing the hollow, but no one knows if that will end up with a win and a loss.

As for after absorbing the hollow, no one knows but Itsuki is certainly stronger however it is still uncertain if he can beat Yamamoto going all out with his Shikai. Yamamoto has the ability to fight all the Gotei 13 captains with just his shikai, while his bankai has the ability to not just kill himself after prolonged usage but also destroy the whole of soul society.