Characters who can easily defeat Sauron are; his Creator Eru Ilúvatar, his old master Melkor, and the Valar. Others who could overcome him would be Ungoliant who physically dwarfed Morgoth, and some great Maiar of Valinor described as almost as great in power as the Valar themselves.
By becoming the true king of Gondor, he also gained access to subtle magic that allowed him to heal Merry and restore the Shards of Narsil to their true glory. He is easily the most influential and powerful Human in the Lord Of The Rings trilogy.
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.
The answer is, by far, Melkor. Melkor, or Morgoth, wanted to currupt and destroy everything good created by the other Valar. Sauron on the other hand only wanted to control and rule Middle Earth.
Why Was Sauron so Powerful? (Even Among Maiar) - Middle-earth Explained
Who is Sauron afraid of?
Sauron's deepest fear was that Aragorn would use the Ring against him. With its powers of domination, Aragorn could comfortably take over the entirety of Sauron's dark army. Though this would eventually corrupt Aragorn, it would allow him to destroy Sauron and take his place.
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.
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.
In the Third Age, he probably considered Saruman as his worst enemy, until he became corrupted. And he remained a threat, seeking the One Ring for himself. But he'd then have seen Gandalf as the chief problem. Someone who constantly caused his plans to fail.
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.
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.
It begins after Sauron's master, the evil lord Morgoth, is defeated. Sauron may have gone into hiding, but he's still alive: the series will eventually show Sauron's creation of the titular rings of power—including the one ring to rule them all.
The man was literally undying thanks to his tie to the One Ring and was so strong that he could continuously reconstitute a physical form even after being destroyed time and time again. With the One Ring, Sauron would have been so powerful that no one could have stood against him.
The first Dark Lord was the rebel Vala first known as Melkor and then as Morgoth. Denied the demiurgic power he desired, he was consumed by a nihilistic purpose: the destruction of Middle-earth. The second Dark Lord was Morgoth's successor, the subversive Maia named Mairon, and later Sauron.
If power includes influence, then Gandalf the White was the most powerful (know power) in Arda, precisely because he is the prime mover in the destruction of Sauron as the Dark Lord. This assumes Gandalf the White was not more powerful than Sauron. The evicdence for this is tenuous.
"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."
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).
Take note, then, that at the root of Gandalf's quest is fear -fear of Sauron in particular. We are not told exactly why -but Sauron is a fellow Maiar, an angelic being who chose to follow Morgoth at the beginning.
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.
In The Lord of the Rings, it is said that had Galadriel chosen to use her powers for evil instead of good, she would have been even more destructive and terrifying than Sauron himself. Galadriel was the greatest and most powerful of all Elves in Middle Earth in the Third Age.
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.
Ultimately, the only being more powerful than Morgoth in his prime was Eru Ilúvatar. Only the combined effort of the Valar could stop Morgoth, and only after countless battles. Sauron might have bested his mentor under certain circumstances, but Morgoth is the greater Dark Lord by every metric.
