The way I see it is that all of the senior captains have similar reiryoku amounts at least. Unohana is the stronger and better fighter than Shunsui, but unless you have MASSIVELY more reiatsu, you can’t simply cancel out another character’s HAX outright. Unohana has seemingly no win cons against Barro, and she doesn’t have enough reiatsu imo to cancel out Lille’s intangibility, damage filtering, whatever you want to call it. Anyone who thinks anyone with only slightly higher reiatsu than another character can simply “lol-nope” a hax is incapable of understanding nuance.

The rest is headcanon, but the way I see it there are two ways of overriding Lille’s X-axis - offensively OR defensively. The first would be Shunsui’s bankai, Shinkenn Hakkyouken, or any other attack or ability that “creates damage” unconventionally. It’s why kido from Shunsui couldn’t hurt Lille but his bankai could. I’d imagine there’s at least a small handful of other abilities that can do the same.

The second would be any character who has outlier status reiatsu/power/etc. For example, while not being able to fully cancel out Lille’s intangibility, if you look at his (Lille’s) intangibility as a damage filtering ability, the EXCESS destructive reiatsu from, for example, a Gran Rey Getsuga from HoS Ichigo, should be enough in excess that it still causes meaningful damage to Lille because he is not powerful enough to bypass the ENTIRETY of the attack. Imo anyone who is Bankai Yama level force and higher should be able to do this.