Personally, I think it's the water gate before his death (without considering the other gods, Izanami and other hanging walls).
First of all, let's talk about Itachi's abilities (before his death): Tsukiyomi (all mainstream illusions), Amaterasu, the third form Susa with an eight-foot mirror and a ten-fist sword (which cannot be maintained for a long time), and the technique of fire escape and shuriken, etc. The weasel's weaknesses are clear and deadly: low chakra levels, self-disease, and vision loss due to overuse of the kaleidoscope.
The abilities of the water gate (before death) are roughly two (commonly used): Flying Thunder God and Spiral Pill. Among them, the Flying Thunder God accounts for seventy percent of the commonly used abilities of the Water Gate, and basically all attacks and dodges are based on the Flying Thunder God, and a typical move is eaten all over the world.
In the case of these two heads-up, the odds of victory for Itachi are slim if they do not include a sneak attack and both sides are ready for battle. First of all, Itachi's fighting style pays attention to quick battles and quick solutions, and it's best if Yueyu Amaterasu can take it away directly, once the battle drags on for a long time, it will fall into the embarrassing situation of *** and lack of blue caused by the body not being able to support the kaleidoscope. In other words, the correct way to defeat the ferret is one word: consumption! (In addition to the strength of direct crushing, such as between the pillars and spots), the longer it is consumed, the smaller the weasel's winning chance.
In this regard, the Flying Thunder God can be said to kill Itachi's death, not to mention ordinary attacks, Amaterasu is no longer good, only try to seize the opportunity to get close to the moon and use it to fight or let the water gate be in illusion at the beginning of the battle. Don't mention Susa.,Before his death, Itachi Kai Susa was basically determined to die.,Itachi can obviously feel that at this time, Itachi's body doesn't have the conditions to control Susa's strength well.,It won't last for a few minutes and it will be counter-devoured and then** (refer to Itachi's first battle) .......So if you don't have the determination to die, Itachi won't open Susa easily.
On the other hand, Watergate, under the correct thinking, there is no need to have too much output in the early stage, and constantly harass, feint, and dodge with Flying Thunder God. This is also in line with the offensive characteristics of the water gate: yin + consumption, as long as the battle is dragged into a protracted battle, the weasel will definitely be distracted due to physical reasons, as long as he seizes the opportunity to plant the flying thunder god seal on the weasel, the weasel has to open Susa's defense (the ghost knows when the water gate flashed behind the Itachi to wipe his neck), and the use of Susa accelerated the consumption of the Itachi.
Therefore, the key to Watergate's victory over Itachi is the continuous flashing and attrition of the Flying Thunder God to fight a protracted war. And Itachi really doesn't have any particularly good ways to fly the thunder god, after all, he can't even catch Quanna's kaleidoscope, and Itachi is not necessarily much stronger than Izumi, not to mention that Itachi's eyesight has decreased a lot.
To sum up, if Watergate can avoid head-to-head confrontation and continue to fight a protracted battle, Itachi will most likely lose, but Watergate will not win easily. Of course, it would be a different matter if you could make the illusion in the water gate in the first place.
Itachi can give Obito a headache and feel that this person is not easy to deal with. Itachi and Obito are afraid of each other, and neither dares to attack each other easily. But in the face of the water gate, Obito's Kamui was explored in just two rounds. This is the crushing of combat IQ and combat effectiveness. If Itachi and Obito are of the same level, then Watergate is at least one level higher than these two.
There is a saying that Obito didn't use all his strength, but even if this is true, the four generations must fight quickly to deal with the Nine-Tails. So I personally think that the two sides are even.
Speaking of illusions, the strongest thing about itachi is illusions, but it is not strong enough to control tailed beasts. Obito's illusion of being able to control the Nine-Tails and the Water Shadow as the power of the perfect human pillar didn't work against the Water Gate. If Obito's purpose is to contain the water gate, isn't it just right for such a powerful illusion?
Moreover, even Kai has a way to deal with the writing wheel when facing Itachi, how can Mizumon not be able to do it?
Besides, Kishimoto's own son, Itachi's ability depends on what the plot needs. Truly. Itachi's new moves all appear according to the needs of the plot. Susanohu sealed Orochimaru, hid individual gods in Naruto's body, and used them on himself by mistake. Then, with the addition of the reincarnated body of the filthy earth, Izanami was transformed.
But if it weren't for the Filthy Earth Reincarnation Body Chakra Infinity, Itachi might not be able to hold on to Susa Nenghu until Izanami was used, and if it weren't for the Filthy Earth Reincarnated Body that could be regenerated, it is estimated that he would have been beaten down a long time ago.
And to promote the plot and save the scene, Watergate is no worse than Itachi at all. First saved Konoha Village and sealed the Nine-Tails at the beginning, then saved Naruto when Naruto went berserk, and then transferred the Tailed Beast Jade at the moment when the ninja coalition was about to be killed by the Ten Tails. Isn't this stronger than a ferret?