The following contains spoilers for Jujutsu Kaisen Chapter 226, "Inhuman Makyo Shinjuku Showdown, Part 4" by Gege Akutami, John Werry, and Snir Aharon, available in English from Manga Monster.
Following on from a chapter that hinted the worst for Satoru Gojo, comes a display of jujutsu proficiency that confirms his standing as the most powerful sorcerer alive. Even after his Domain Expansion was destroyed and he suffered the consequences of Malevolent Shrine's guaranteed hit effect, Gojo has refused to accept defeat at Sukuna's hands, passionately clinging to life using a combination of skills that no one else could manage.
Domain Expansions are harmful because people imprisoned within its limits are in a region completely controlled by their opponent. In Ryomen Sukuna's situation, Malevolent Shrine's territory is continually influenced by his slashing cursed skills, Cleave and Dismantle. The fact that Gojo wasn't shredded right away is a tribute to the massive amount of cursed energy he still has at his disposal, especially when contrasted to Special Grade Cursed Spirits, one of which couldn't live even a second in Sukuna's Domain.
Gojo Survived Sukuna's Domain With Reverse Cursed Technique
Gojo's response to the initial slash that threatened to decapitate him was to rapidly repair the neck damage with positive energy derived from reverse cursed technique. Nonetheless, the fact that Malevolent Shrine was still active meant that he would continue to suffer comparable afflictions as long as he was within range of the Domain. Even with this additional handicap, Gojo was able to manage both healing the repeated slashes and battling physically with Sukuna.
Even if his recuperation was instant, fighting Sukuna without a cursed technique was unsustainable. Gojo deployed a Simple Domain to give himself some breathing room after ascertaining that he could resist Sukuna's strikes without the healing factor of reverse cursed technique, and then diverted his regeneration into his standard cursed technique. His unusually huge Simple Domain was remarkable enough, but to refresh his cursed technique, Gojo literally did the equivalent of plugging an extension board into itself and miraculously generating electricity. It should have been impossible, but when has the Honoured One ever followed the rules?
Gojo's Cursed Energy Reserves Are Much Larger Than Previously Anticipated
Whether it's through his Six Eyes' optimization or an additional effect of the buff Utahime granted him at the beginning of the fight, Gojo's feats so far have consumed more cursed energy than most sorcerers could boast of on their best days. So far, Gojo has used a Hollow Purple powered up to 200% of its base potential, opened a Domain Expansion, activated both Blue and Red in succession, and finally healed his entire body with reverse cursed technique, which uses double the amount of cursed energy traditional jujutsu consumes. He hasn't broken a sweat even though most sorcerers would have been instantly defeated after losing a domain battle.
Despite the number of devastating techniques they've unleashed on each other, Gojo and Sukuna appear to be just getting started in Jujutsu Kaisen's eagerly anticipated duel of titans. Gojo has already exhausted the pool of techniques he's been confirmed to have in the series, so any surprises he has in store are just around the corner. Sukuna's mystery bag of tricks has also not been opened in the least. There's been no indication of the flame-based skill he demonstrated during the Shibuya Incident, or the Ten Shadows he recently obtained by snatching Megumi Fushiguro's body. Both fighters appear to be feeling each other out before committing to a very powerful attack, thus their battle could be one-sided.
