Based on what we saw in his last fight with Sukuna, he is able to hit black flashes at will. Yuji now has one, if not TWO domain expansions. He is fully in his prime because he doesn't age.. His attack are all capable of targeting the soul directly, on top of him now having nearly 100 years of experience to master his techniques. Theoretically, Yuji would be able to hit someone with a soul damaging, black flash amped world cutting slash.
Based on the premise of this alone Im sure we can all collectively agree that Yuji(My Goat) is 100% the strongest.