No doubt Itachi could've killed Sasuke quickly in the match if he had use Susanoo, but we all know that he has Susanoo. I don't understand how that makes him stronger.
Itachi don't have the chakra to rival madara
Itachi doesn't need chakra to rival Madara. Gai didn't have the chakra close to Kisame's level but still won. Naruto was disabled from using his chakra but still beat Neji.
We don't know what his true strength is. Fact is, he's a lot stronger than he's shown in the manga, he wouldn't need new jutsu or a boost for that.
Stronger version of his attacks, more jutsu, etc. Every time Itachi has fought, he has never gone full out. Against Kakashi, he wasn't using full power as confirmed by Kakashi. When he was fighting Sasuke, Itachi was sick and holding back enough to challenge Sasuke. He didn't want to fight Naruto or Bee, and when he sealed Nagato, it was Nagato controlled by Kabuto. Itachi also didn't go all out against Kabuto considering he needed Kabuto alive.
Plenty of ways to deduce how he's stronger.
What you said doesn't mean anything because we all know what happened.
By killing kakashi does that make him stronger? No. He defeated him the same way in the same time Fram, with the same jutsu.
Killing Sasuke, does that make him stronger? No. We all know he could've killed Sasuke by bringing out Susanoo at the begining of the match.
If Itachi Susanoo level up Like Madara, then how can he be stronger. More jutsu doesn't make you stronger if you don't need to use them, or the jutsu isn't worth using.
Fact is Itachi never went all out, but the only difference that makes is he best his opponents quicker and lose slower to the ones he could beat...
Lol I'm tired, so we can agree to disagree.
1) Obito jinchuriki of the Ten Tails
2) Edo Madara
4) BSM Naruto
5) EMS Sasuke
8) Six Paths of Pain
Out of the top 10 in Naruto other really strong characters in my book are Tobirama, Kabuto with SM and Edo Tensei, Might Guy, Killer Bee, the Raikages and the Tsuchikages.
naruto with full kyuubi/sage mode combined
obito with ten tails
dragon sage mode kabuto