Didn't seem all that impressive. That hydra form was getting its heads sliced off like nothing against Itachi, before getting sealed. That hydra just showed how slow and unimpressive it was. Yes itachi and his susanoo is beastly, but Itachi quickly/easily defeated Orochimaru on two occasions, which is funny because itachi wouldnt fight jiraya because it was an unnecessary risk, since itachi himself said the best he could do against jiraya would be a stalemate...
Seriously bro read manga again oro hydra was overwhelming the Susanno all the Susanno could do is chopp it's heads off and they grew right bak instantly also releasing w.e tht stuff was into the air and did a snake like TBB it was like a bijuu IMO all itachi could do was seal the hydra cuz he couldn't kill it cuz the hydra just kept regenerating and started rapping it's heads around the Susanno
Once it started overwlehming Susanno oro started doing speech (stupid of him I admit) and then itachi started sealing it
And tbh tht is a plot hole If u read the toswaka sword bio thingy it says anything it touches it automatically seals so why was itachi able to use it as a physical sword ???? When it's suppose to be a spiritual weapon in fact it's suppose to be the opposet of sword of kansanji while tht one is physical sword toswaka is suppose to be spiritual?? Tht doesn't make since at all I hate kishi and his favoritism -_-
Tht weapon shouldnt be able to cut anything physical sealing is one thing if Thts the case it shouldve started sealing oro once it touched hydra
But anyways hydra is freaking awesome u say it's slow it moves exactly how oro or a snake does patiently then moving its heads in fast pace to capture and subdue its victims example itachi's susanno