Sasuke's Monstrous Strength was naturally something he learned from Orochimaru. With such an exceptional physique, it would be a waste not to master a formidable style of taijutsu.
Fighting strengths with weaknesses, Itachi was certainly no match in pure taijutsu, but Susanoo was no joke either—even Tsunade would find it somewhat difficult to shatter Susanoo.
Sasuke's current self definitely couldn't reach the terrifying level of Tsunade, but he could still trade blows with Itachi for a short time.
Chapter 358