Sauron's evil grew from his original servitude to Morgoth, the world's first Dark Lord, into his own obsession for "mastering" all things in Middle-earth through wicked means. After Morgoth's fall, Sauron was fully autonomous and committed, for two Ages, to gaining tyrannical control over Middle-earth.
He explained that, like "all tyrants", Sauron had started out with good intentions but was corrupted by power, and that he "went further than human tyrants in pride and the lust for domination", being in origin an immortal (angelic) spirit.
What Makes Him Pure Evil? While he was once a force for good and one of Gandalf's best friends, his lust for power along with getting fed up with defending the weak consumed him, making him a Social Darwinist. He later in the Lord of The Rings, betrayed Gandalf because he believed that Sauron would be unstoppable.
The corrupting effect of power in the book is not limited to the Ring. Sauron was already corrupted when he chose to put much of his power into the Ring to gain further control of Middle-earth.
Originally known as Melkor, Morgoth is essentially the Lucifer of Tolkien's story. Like the devil, Morgoth was one of the first children created by the God of Tolkien's world, but succumbed to jealousy and greed, especially over the creation of other races, and was duly disowned by his fellow Valar.
Melkor is the most powerful of the Valar but he turns to darkness and is renamed Morgoth, the primary antagonist of Arda. All evil in the world of Middle-earth ultimately stems from him. One of the Maiar of Aulë betrays his kind and becomes Morgoth's principal lieutenant and successor, Sauron.
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.
Sauron seemed to genuinely feel a connection to her, and part of that came from sensing the darkness inside of Galadriel. In that regard, his offer was really a seduction to the dark side.
Despite her power, Galadriel couldn't match Sauron's ability to wield the One Ring, and it would have ultimately turned against her. Even if she managed to carry the ring, Galadriel's ambition and power-seeking nature would have eventually led to her corruption, making her unfit to deal with Sauron's weapon.
Saving Galadriel at sea was likely a method of gaining her trust, since Sauron would need an Elf's friendship to enter their realm. Whether he targeted Galadriel specifically because he could exploit her bloody-minded rage and broken heart is unclear.
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.
The majority of her powers come from her Ring of Power, Nenya, the Ring of Water. The ring, also known by the names the White Ring and the Ring of Adamant, is one of the three Rings of Power given to the Elves of Middle-earth in the Second Age.
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.
"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."
Morgoth is the more powerful of the two. Morgoth was the mightiest of the Valar, a group whose weakest member would outpace Sauron. However, there are some circumstances and eras in which Sauron would win the day. Morgoth was born far beyond Sauron but lost and surrendered much of 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.
Saruman fell primarily from excessive pride and envy. He was proud of his position as leader of the Istari and jealous that Gandalf got the Elven Ring from Cirdan and not himself. He saw himself as the “expert” on such rings, and likely saw this as a deliberate insult.
She also resisted being offered the ring of power by Frodo following his vision in the mirror of Galadriel, an immense test given the ring's seductive powers. Yet Gandalf's power level exceeds even that of Galadriel, as shown by his rebirth in the Two Towers.
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.
For those that haven't read Tolkien's work, it's easy to see why many audiences suspect Gandalf and Galadriel are in love. After all, many of their interactions in The Hobbit trilogy practically scream romance. However, their relationship remains purely platonic in Tolkien's source material.
Thus, Galadriel's dark form in Jackson's The Lord of the Rings personified what would have occurred had the Lady of Lothlorien given in to temptation and taken the One Ring for herself. She would have succumbed to evil because the Ring was indomitable, even with her power.
Meanwhile, a few faithful Númenóreans, led by Elendil, were saved from the flood, and they founded Gondor and Arnor in Middle-earth. Sauron still considered them his hated enemies and he launched a pre-emptive attack on Gondor in S.A. 3429.
Isildur used a broken sword to cut the Ruling Ring off Sauron's hand. Sauron was fatally wounded by Gil-galad and Elendil as Sauron killed them. Gandalf took the job of blocking the Balrog - and he was barely able to defeat the Balrog (in fact, he died in the process).
