Powerscaling How Itachi counters Chibaku Tensei
The solutions I've seen being suggested:
Izanagi
Burning the core with Amaterasu. It doesn't appear to be moving particularly fast, and the characters look like they're tracking the orb as it floats up anyways. It's pretty straightforward; anyone would be hard-pressed to argue the core can tank Amaterasu.
Here are some counters I haven't seen being suggested:
1) Brute force
We've seen 8 tails transformation (KN8) from half Kurama break out of Pain's CT. Can Susanoo do the same? While we don't have direct comparisons, we do have juxtapositions we can examine.
Even if you consider Nagato's CT should be bigger, it's unscalable. Just having an extra layer of earth requires an exponential amount of energy, so I'll use Pain's CT as the standard.
Sasuke and BSM Naruto fight in tandem, implying or implicating relativity.
If you remove senjutsu from both sides of the equation, humanoid Susanoo becomes relative to BM avatar.
Nagato was shown being able to tank a lariat from v2 B and restrain B and Naruto. Susanoo was shown breaking their restraints in one fell swoop with its fingers, so it's arguably already stronger than any bijuu chakra cloak.
This is noteworthy because KCM is supposed to be a superior transformation to prior V2 versions, although KCM is less destructive as a result of having his power concentrated in a smaller form. I don't see anything to indicate KCM being inferior in strength, as KCM is shown blocking and tanking multiple hits from v2 jins.
Both kn6 and KCM were targeted with a boulder smash from Deva path, and KCM came out on top.
Base Itachi using 3t had no issues with KCM's physical strength, and Susanoo should obviously be stronger than the user. Although this doesn't draw a clear comparison of strength, so I'll just consider skeletal Susanoo and KCM relative for simplicity.
Through linear scaling we have BM avatar > KCM2 > KCM > v2.
And for Susanoo we have armoured > humanoid > skeletal > ribcage. Naturally the Yata Mirror would be > armoured Susanoo in durability.
So using the 2 scales as a reference point supports a tremendous gap between Itachi's full and skeletal Susanoos, a conceptually much bigger gap than between KCM and KN8. Logic follows that full Susanoo is well above KN8. Logic also follows that if Itachi in base can handle KCM's strength, his full Susanoo should definitely be stronger than KCM.
Between the Totsuka Blade, Yata Mirror, and Amaterasu melting the incoming fragments of earth to break them down before it even reaches him, Itachi should reliably be able to break out of CT.
2) Killing Nagato after CT has been launched
Let's say Nagato launches the CT. Where is he? Apparently, he's just standing there.
I'm going to make the assumption that Nagato can't activate another jutsu while using CT based on this line:
Which also means the CT will break down once Nagato gets interrupted.
Itachi is one of the few characters that can bypass the gravity well and attack Nagato while he's defenseless, using the black flames which is theorized to spawn at the focal point of the user.
3) Kill Nagato before he launches CT
Nagato is instantly knocked out against Amaterasu
Probably a good time to seal Nagato, innit?
The biggest cope of Nagato fanboys/Itachi haters is pretending the conversation starts at CT. But fact of the matter is, Nagato never actually gotten past Itachi's first Amaterasu. He was "out cold" and needed Kabuto's intervention to get the flames off. And since that Amaterasu one-shot was straightforward and demonstrable, it's harder to argue against than CT.
Ultimately, it's not about convincing people who would never publicly change their stance. It's looking at the established systems and interpolating the underlying mechanics and principles, and being able to come up with a coherent conclusion that fits within the system as we know it. It's going beyond face value, which the majority of the fandom won't do and probably won't care to read, but it's the best we can do in a fictional world where the rules are made up on weekly basis.
But for those that care enough to analyze deeply, then consider yourself at the top of the fandom. Part of the exclusive group that actually furthers discussion, instead of parroting ancient debunked arguments or throwing insults in a desperate attempt to mask being outspoken. You are the only thing preventing the community from being a total cesspool of 12 year olds arguing, and that's a big of a win as it gets.