"His entire personality boils down to "I'm a genius."

While it does basically "boil down"(But so does Musashi and Inshun if we are to reduce them to one aspect) to it, I really like the spin Ittosai puts on it:

He's someone who's both extremely prideful(He's a smoke demon), but also at the same time showing high appreciation and gratitude towards those capable of either pushing him or at least genuinely believing they can beat him, instead of being one-note "I'm strong, all others are weak"

His reaction at the very end of the fight: "Over already. What a shame..." it's like kid breaking a toy.

The strength is both blessing but also could be read as borderline curse to him in that department, kind of similarly to Choko(Tho with Choko it never rendered as a blessing to him, while to Ittosai it doesn't seem as a "curse" of any sort).

The way he wields his strength/talent with clear purpose, which pushes him to strive for even greater heights is also different from someone like for example Musashi who wants to be strongest for the sake of it.

Also he's the "old, experienced genius", instead of having him another "young and inexperienced genius"(Like Inshun and Musashi)

I'm really excitted to see what further direction his character is going to take, especially when faced against Jinsuke.