Sauron was a servant of Melkor, later known as Morgoth, who is mentioned in 'Rings of Power', basically Lucifer of Middle-earth who brought terrible destruction upon the earth and waged the greatest war against elves.
As "Gorthaur" he became the most trusted lieutenant of Morgoth, being reckoned as the greatest of his allies and servants in the Wars of Beleriand. From his fortress of Tol-in-Gaurhoth, Sauron was directly responsible for the death of Barahir and later the Noldorin king Finrod during the Quest for the Silmaril.
He was originally the Istari's chief, and was head of the White Council that for a time opposed the Dark Lord. But by the late Third Age, Saruman was overcome by lust for power and swore fealty to Sauron, becoming one of his greatest servants.
Sauron hated the way Arda was run. He was the enemy of the Valar, because he thought they did a poor job organizing it. Morgoth was the GREATEST enemy of the Valar, and the most awesome being in the universe, and thus he became Sauron's boss.
However, the mere fact that the Valar didn't prioritize perusing Sauron proved he was a much lesser threat than Morgoth. It made perfect sense because Morgoth was a Valar, and Sauron was only a Maia. So, while Sauron was evil, Morgoth was clearly much worse.
Bloodlines are very important in Tolkien's stories, and it makes a lot of sense that Sauron would fear the great-grandson of the man who cut off his hand. Aragorn carried the blood of Numenor with him. His genetic connection to the heroes of the Second Age established him as a dangerous opponent of Sauron.
The outcome is that Galadriel is able to penetrate Sauron's mind and issues a single command "Go back to the void from whence you came!" Unable to resist her any longer, Sauron screams and flees with the Nine.
Sauron's only interest was an order or to work upon the world in an orderly state, even in the beginning, Mairon really had no love interest. Despite his deceptive attributes, he was a trickster and a seducer, he had little care for attempting to love someone.
He is described as being equal in power to Manwë, chief of the Valar in Arda. But his power increases in later revisions of the story until he becomes the most powerful among them, and in a late essay more powerful than all of the other Valar combined.
Morgoth, the first to reign terror upon Middle-earth, was more powerful than Sauron and commanded an army of dragons and Balrogs. While both Morgoth and Sauron were cunning, Morgoth's rule and terror lasted longer and his corruption spread further, making him more formidable in the Lord of the Rings universe.
Melkor (Quenya: "He who arises in might"), predominantly known as Morgoth (Sindarin: "Black Foe of the World"), was the rebel Vala, the first Dark Lord, and the prime mover of evil in Eä in the Elder Days. Since he could not control Arda, he sought to reduce it to a formless chaos.
"So I think in his pitch to Galadriel, it cannot mean that he loves her or that there's any kind of romantic relationship. There should be no ambiguity around the fact that Sauron is evil — he's terrible, and he's using Galadriel to enhance his power."
Additionally, while he was in his weakened state, Galadriel could hold him off through the power of will alone. However, if Sauron had his One Ring and faced off in a battle against Galadriel, it's unlikely that there would be much she could do.
In his notes, Tolkien remarks that Sauron saw Galadriel as his equal. Add that to the fact that she's untrusting of Sauron (yes, even when he's in his Annatar guise) and an unwavering, single-minded force, and it's more likely than not that Sauron feared Galadriel — or the potential she held to upend his plans.
Sauron is an expert manipulator and likely sees Galadriel and her power as an asset. In line with the old adage, "Keep your friends close; keep your enemies closer," he'd rather have her on his side than against him.
Assuming the One Ring was destroyed, Galadriel's ring would also start to fade, causing Lothlórien to lose its glory and magic. So, when Galadriel refused the One Ring, she wasn't just sacrificing her desire to rule. She knew that she was sacrificing her kingdom and its well-being for the sake of peace in Middle-earth.
Although Sauron's origins are angelic, he becomes captivated by the idea of ordering things as per his own will, which might be a possible reason behind him being lured by Morgoth, a Dark Lord who corrupted countless souls and waged wars against Elves and Men throughout the First Age.
Finally Sauron came out to fight Elendil and Gil-galad face to face. When Elendil fell, his sword Narsil broke beneath him. Isildur took up the hilt-shard of Narsil and cut the One Ring from Sauron's hand, vanquishing Sauron.
Galadriel was very close to her brother Finrod, who could be seen in episode one of The Rings of Power, and when he was mortally wounded by a wolf of Sauron, Galadriel swore vengeance. She, like her Lord of the Ring's parallel, had a deep sense of right and wrong, of light and dark.
Aragorn and Legolas are long-time companions and best friends since Legolas' father Thranduil sent him to live among the Rangers of the North. Aragorn and Legolas grew close, up to the point where Aragorn revealed his true identity to Legolas. Throughout his journeys, Aragorn and Legolas are as close as brothers.
