Currently, Jigen is the strongest known character in the world of Boruto. His powers were great enough to take on both Naruto Uzumaki and Sasuke Uchiha at the same time. As the fight between the two unraveled, Jigen's superiority over both Naruto and Sasuke became quite apparent.
Naruto ended the Fourth Great Ninja War being much stronger than Sasuke as not only did Sasuke lose the power of the Tailed Beasts but Naruto also received the other half of Kurama, giving him even more strength and chakra.
However, when it comes to genjutsu, Itachi definitely has the upper hand, and that alone is enough to defeat Sasuke. His knowledge of the Sharingan also surpasses Sasuke's. It's Itachi's prowess with genjutsu that Sasuke never seems to match. In fact, Sasuke seems to be mostly powerless against it during their battle.
1) Obito Uchiha
However, Obito can't defeat Sasuke, as the latter, after receiving chakra from the Sage of Six Paths, became stronger than him and was able to fight against the likes of Madara and Kaguya.
5 Would Crush Him: Sasuke Uchiha
Like Naruto, Sasuke became powerful enough to fight Madara Uchiha in his Six Paths form without much trouble, which just goes to show that he was stronger than Guy and would Crush him in battle.
Sasuke would have only won by outlasting Itachi, and if the latter had no reason to hold back then he would have gone all-out. When the two brothers fought against Kabuto, it was only because of Itachi's knowledge that they managed to defeat him.
In addition, Kakashi had always been an intelligent strategist, and he just might be able to best Itachi Uchiha in single combat after getting that second Mangekyou Sharingan eye.
9 Can't Beat: Luffy Has Nothing To Counter Sasuke Uchiha
Sasuke is arguably one of the strongest rivals Naruto has ever faced. Aside from his incredible hand-to-hand prowess, Sasuke is a great strategist capable of creating complex battle strategies on the fly, making it very likely he can outsmart Luffy.
Hashirama Senju, aka the First Hokage, was the only one who could ever beat Madara Uchiha in life.
Itachi Uchiha is the single most powerful character in the Naruto Universe. Masashi Kishimoto named himself Itachi Uchiha. He unlocked his power at a very early age, for example, unlocking his Sharingan at a very early age. When he was 11, he joined Anbu black ops.
It is easy to see that Sasuke supplants Madara in every category except for chakra reserves as the latter was the jinchuriki of the Ten-Tails. However, Sasuke is far ahead in all the other categories. Consequently, Sasuke is undoubtedly the strongest Uchiha in Naruto.
Sasuke was stated to be the strongest Uchiha to ever have been born, including Madara. So, obviously, his powers do exceed Madara's. With his Choku-tomou Rinnegan and Indra's arrow, he is almost invincible. As a result, he is also one of the Naruto characters who can defeat Madara.
All things considered, Tsunade Senju is certainly the weakest Hokage age in the Naruto series as not only is she the weakest of all the Sannin but is also way beyond her best days during her time as the Hokage.
10 Could: Itachi Uchiha
Itachi was able to fight against Naruto Uzumaki in his Nine-Tails Chakra Mode, something that Pain could never do. He was also able to incapacitate Nagato Uzumaki, and it is quite easy to see that he could definitely have taken on and defeated Pain in combat.
Shisui Uchiha
While the ability itself was powerful, Shisui failed to ever demonstrate its proper use. Furthermore, he lost this eye to Danzo, proving once again that he wasn't as strong as some of the others.
Luffy's Gear 5 makes him incredibly powerful, more than most Naruto characters. In fact, it's arguable he could defeat all of them, bar the absolute strongest ones.
Naruto Possesses Massive Firepower
In his base form, Naruto is immensely strong. However, when he combines his Six Paths Sage Mode and his Kurama Mode, he is stronger than anything Luffy will ever face. Even if Luffy were to get 10 more Gears, he still wouldn't be strong enough to stand up to Naruto in this mode.
Sakura Haruno: Sakura's punches would damage Luffy even though he can act as rubber. There's no way he can dodge her brute strength and make out of the fight alive.
Despite this, she pales in comparison to Kakashi Hatake. Kakashi is a very fast, and shrewd shinobi, so for him to let Tsunade hit him in the head is preposterous. Furthermore, Kakashi's offensive powers, such as Kamui, far surpass that of Tsunade's. If the two ever fight, Kakashi would emerge as the victor.
However, if the Boruto two characters went up against each other, Kakashi would win despite losing his Sharingan. Kakashi losing his Sharingan means he cannot copy the ninjutsu that the enemy performs.
Taking all things into perspective, Kakashi is unarguably one of the most complete shinobi in the entire Naruto series. Might Guy, on the other hand, lacks the ability to perform a Genjutsu for use strong Ninjutsu.