Naruto is considered one of the most popular anime in the world. We all have a special memory attached to the series. Released in the year 2002, it continued till 2017 and became the most popular in the world.
The series is versatile, to say the least, with its variety of characters, clans of shinobi, plots twists, backstories, tragedies, and so on. The story starts with the narration of the events that took place in Konoha over a decade ago.
A few years back, Konoha was attacked by the legendary nine-tailed beast which resulted in several casualties. Even the fourth Hokage, Minato lost his life in the battle with the beast. However, before he died, he sealed away the nine-tailed beast inside the body of an infant who was later revealed to be Naruto, Minato's son.

The entire plot revolves around the development of Naruto being raised in the face of criticism and ostracization. He rose through those circumstances and made a name for himself as the village's hero. However, the tailed beast inside of him remained as an obstruction for the entire series.
Naruto had to train himself to stop Kurama from taking control of his body. It wasn't until the final arc when the Fourth Great Shinobi War started that we found out about Kurama's past and his perception of humans. Here, we will discuss the reasons why Kurama was perceived as a villain for the most part of the series.

Kurama's Life Before being Sealed Inside Naruto
Born from the power of the ten-tailed beast, Kurama was one of the nine beasts and the strongest one at that. After the defeat of the ten-tailed beast, the Sage of the Six Paths made himself its Jinchuruki and sealed the monster inside of him.
However just before he was about to die, he divided the power of the ten-tailed beast into nine beasts, each having a different number of tails, which also signified their strength.

For example, the beast with one tail was the weakest and nine tails were the strongest. He and the others were soon emotionally attached to the Sage and were lonely after his death. The legendary battle between his two sons, Asura and Indra, was the start of Kurama's tragedy.
Indra is the ancestor of the Uchiha clan and they all have the ability to control the strongest tailed beast to make them do their bidding. Indra forcefully used Kurama in his fight against Asura. Since then, the tailed beasts scattered among the world.
Centuries later, the tailed beasts were forced to be sealed inside powerful Shinobi and were used as a means of establishing the power of a particular clan or a village.

Kurama ended up in the Uzumaki clan, the distant relatives of the Senju clan (Asura's descendants). Uzumaki clan was known to have more chakra and unique abilities than the other Shinobi.
Their tremendous chakra made them a suitable host for containing the power of the nine-tailed beast within their body.
By the time Hashirama Senju was building the Konoha village, he married the first Jinchuruki of the nine-tailed beast from the Uzumaki clan. Since then, Kurama's powers were used to signify the power and stability of Konoha.
Naruto's mother Kushina was chosen as the next Jinchuruki and then it was Naruto's turn. By the time Kushina became the Jinchuruki, the Uzumaki clan was already annihilated in the war.

The Attack on Konoha

The attack of Konoha was a tragedy to be remembered. Kurama wreaked havoc in the village, killing even the strongest of the Shinobi. No human was capable of containing the embodiment of the hatred itself. After the several sacrifices and Kurama being forced to get sealed inside Naruto's body.
The village quickly got back to its feet with the Third Hokage being reappointed as the Hokage after his retirement. The nightmare seemed to have ended on the surface with the village being united as strong as ever.

However, the hatred they had towards the nine-tailed beast was automatically transferred to the infant who was used as a host of the beast. Naruto grew up never knowing why he was ostracized and learned the truth about the beast being inside him much later in his life.
It wasn't until later that the truth behind the attack was found out. Kurama was summoned by Obito Uchiha, who was impersonating himself as Madara. Obito had absolute control over Kurama and being under the manipulation of the Mangekyou Sharingan, Kurama was forced to be the weapon in an elaborate plot.

The Embodiment of Hatred
Being controlled, used, and chained, Kurama suffered for centuries at the hands of humans. The humans were much weaker than him, but they always had new tricks to keep him in check. He was being forced to do the bidding on behalf of the Uchiha clan and then being controlled by the Uzumaki clan.
At some point in his life, he started having deep resentment towards the humans even to the point of describing himself as the living "embodiment of hatred". His intense hostility and distrust towards humans only faded after he became friends with Naruto.
Kurama's every action in the series, whether it was the attack on the village or his several attempts to take control of Naruto's body, hinted at the fact that he was, in fact, evil. The fact that he became the embodiment later in his life was the result of the human's treatment of him.

Since Kurama was not a human, his tragic backstory is often underrated. He was forced to do the dirty deeds for others and criticized for it. This is why Kurama was perceived as a villain for the most part of the series. Even though his actions at the beginning weren't exactly honorable, he was nowhere near being evil.
His friendship with Naruto was also extremely deep. After the war, all the tailed beasts decided to fulfill their dreams and live free from them. However, Kurama was the only one who decided to stay inside Naruto and watch over him for the rest of the latter's life.