Sauron

Sauron is the main antagonist and titular character of the Lord of the Rings films.

Pre Lord of the Rings
Sauron was once the lieutenant of Morgoth. However, he broke a way when his master was defeated and forged rings for each race, Elves, Men, and Dwarves. He had his minions destroy half of Middle-earth, however, the Elves and Men united together. During the fight,  he killed King Elendil with Isildur watching. He took his killed father's sword and used it against Sauron. During the struggle, Isildur was able to chop off Sauron's ring finger as Isildur took the ring.

Personality
Sauron is ruthless and pure evil. He did not care for the welfare of others. He was also deceptive. Sauron could take any form to deceive the Elves, the Dwarves and the Men.

Trivia

 * Characters that have communicated with Sauron have been (in order of release) Saruman, Pippin and Aragorn. In The Hobbit, Azog, Galadriel, Gandalf and Elrond later communicate with him during The Battle of the Five Armies.