Sauron

Sauron is the Big Bad Evil Guy of the Lord of the Rings franchise and the reason behind much of the changes and upheaval that the LoR world has faced during it's current ages. He is one of the first proper Dark Lords in popular fiction; while Voldemort, Doctor Doom and Abaddon were in kindergarten like some evil version of the muppet babies learning what the word 'bad' meant, Sauron was out cracking heads and getting shit done.

He wasn't the original big bad for LoR, oh no

A hilarious note is the fact he wasn't even the big bad to begin with; Morgoth the first Dark Lord seduced Sauron into his new lifestyle by offering him unlimited chocolate cake forever and Sauron agreed, quickly becoming his chief underling. Once his boss was beaten up by the other Ainur (Tolkien's versions of archangels in this universe), Sauron fled across the sea to middle-earth, where he used his great cunning and sorcery to work events to his favour. He corrupted the Nunemorians (the LotR equivalent of Atlantis) and caused so much harm the other Maia used their full power and sunk Numeor; an action which made Eru (the LotR equivalent of the Judeo-Christian God) to forbid them from using their full power to reduce collateral damage.

Damn those pesky kids!

Like any true evil villain, Sauron was then beaten time and time again but he always managed to flee while screaming "I'll be back" over his shoulder. Finally having enough for the subtle methods, he tried to merely maul everyone to death in his big destroyer form with an army of orcs but thanks to some pesky men and elves, he got his finger with his magic ring (which contained a great deal of his power and life) cut off and as a result became a highly pissed off spirit that kept trying to come back, knowing that if he could get his bling back again he could have another bash at taking over the world.

Rise and fall again, this time for good

Sauron managed to crawl (do spirits crawl?) his way back from the abyss through sheer stubbornness and over time rebuilt his strength. When he felt secure enough he returned to his dark kingdom Mordor and began preparing for his final war against the kingdoms of men and elf, breeding an army of SUPER orks to do his bidding. But you remember that bling we mentioned earlier? Some dang pesky hobbit kid only went and dropped it in Mount Doom! The one volcano that could destroy it! You know what we are saying?! Yep, it was bye bye for good this time Sauron and the one guy who made the world interesting popped his cogs.

And everyone went home in time for tea.