Surprisingly, Kakashi is also one of the many users of the Rasengan. In fact, he mastered this technique at quite a young age. Just like Minato, Kakashi tried to add his nature transformation to this
First of all, Rasengan is a jutsu which doesn't require hand-seals. It's just a manipulation in chakra release. Hence, it can't be copied using a sharingan. Hence, Kakashi didn't copy the rasengan.
It remains unknown how Kakashi learned this Jutsu, or who taught it to him, but it is speculated that it has to do with his Sharingan. This is because the Sharingan grants him the power to copy Jutsu at will, as long as they're not Kekkei Genkai or Hiden abilities.
Similarly to Chidori, Rassengan is an iconic jutsu in the Naruto series. While audiences never see Kakashi use this attack in battle, the sheer power of Naruto's signature move is almost unmatched. With the ability to end opponents in one hit, the fact that Kakashi can use both this and Chidori is truly frightening.
It is said that Minato did teach Kakashi the Rasengan, and respectively, The Chidori was created as Kakashi only applied his lightning release/nature to it.
Kakashi is a master of over a 1000 jutsu but these are some of his rarest techniques.
However, Kakashi was shown to be a ninja prodigy even before he gained the Sharingan, meaning the statement of Kakashi being weaker without the Sharingan is an unjust assumption. Analyzing his current skills and achievements reveals how strong he truly is, even without the visual jutsu.
Despite not being able to copy jutsus in the Naruto series, he still has access to over 1000 jutsus that he copied when he had the Sharingan. Fans are aware of the fact that Lightning Release is stronger than Earth Release, but Kakashi managed to improvise an Earth Release technique that is unaffected by lightning.
The Chidori was created by Kakashi Hatake after he failed to apply his lightning-nature to the Rasengan. He intended for the Chidori to be a weapon used only to protect friends and loved ones.
For this reason, most ninja cannot use the Chidori safely. However, a user of the Sharingan can overcome these drawbacks due to its heightened visual perception preventing the tunnel vision from occurring and its predictive capabilities making it easier for the user to avoid counterattacks.
After losing his Sharingan in Naruto, Kakashi replaced Chidori with its lightning-based counterpart named Purple Lightning, which is nearly identical but without the speed boost and piercing power. Unlike Chidori, Kakashi is able to use Purple Lightning in both close and long-range fights.
Kakashi using Rasengan. Kakashi primarily relies on his mastery of ninjutsu, possessing both great skill and otherwise knowledge of which he has gained a vast arsenal due in part to his Sharingan; being noted to have copied over a thousand techniques, the number has continually been growing through his many battles.
The Rasengan uses no hand seals and is based upon expertise with Chakra control. Despite all the answers about its incompleteness and how Sasuke “doesn't need it” and so on, that is all nonsense. He could not copy it because, like Shadow Clone, it's not a technique that can be copied.
As I stated earlier the Sharingan can imitate the hand signs of an opponent but the Rasengan did not require any hand signs so it would have been hard for Sasuke to "copy" it if he did not know what to do.
As has already been established, the weakest Hokage of Konohagakure is between Kakashi Hatake and Tsunade Senju. In fact, both Kakashi and Tsunade are quite close to each other in terms of strength in Naruto. However, their fighting style differs a lot from each other.
One of the Three Great Eyes in Naruto, the Rinnegan eyes are the strongest of them all.
Sakura Haruno is a skilled shinobi who boasts considerable physical strength. But she really shines in the field of medicine as she was trained by the greatest medical ninja of all time, Tsunade. However, if the Boruto two characters went up against each other, Kakashi would win despite losing his Sharingan.
One of the strongest known Kekkei Genkai in Naruto, the Rinnegan is the rarest of the Three Great Dojutsu. This eye holds tremendous significance in the Naruto world and it is believed that those who hold this eye would either bring great destruction or a great change in the world for the good.
A very simple technique with an over-dramatic name, One Thousand Years of Death is little more than inserting one's index and middle fingers (similar to the Tiger hand seal) into the opponent's rectum, causing constipation, pain and/or embarrassment. It has no effect on unconscious targets.
1 Kamui Raikiri
Kamui Raikiri is the strongest known Jutsu of Kakashi Hatake. Combining the powers of Kamui with that of a Raikiri enhanced with Six Paths chakra, Kakashi was able to create a surefire technique powerful enough to injure even the likes of Kaguya Otsutsuki.
Kakashi's signature move is Raikiri, which he used to kill Kakuzu, and during his fight with Obito, he used it to pierce his heart. Sasuke's Chidori was taught to him by Kakashi, to which he then made various improvements.