
As much as I hate his character, Feanor is the one. The making of the Silmarils and their subsequent theft was the catalyst for all that came afterward. The Flight of the Noldor is what brought about the different ages of Middle-earth. Were it not for Feanor's anger and hatred, the kinslaying would not have occured. You would have had no Doom of Mandos and who's to say whether there would even have been a second and third age but for the actions of Feanor during the First.Originally posted by Ceorl
Without a doubt the most influential single non-Ainu character has to be Feanor. If he had not done what he did, then the Noldor would not have left Valinor. Thereby the entire Silmarillion would not have happened. The Valar would not have the problem of not being able to contest Morgoth due to their banishment of the Noldor, and they would have destroyed Morgoth(and probably Sauron too) much earlier for the sake of the Atani. the Atani would not have fallen(mainly) under the domination of Morgoth, and later Sauron, there would have been no Numenor, and no Noldor in ME. that erases the second Age. In the third age all the Atani would be united against Sauron(if he had survived) and would easily have destroyed Sauron even without the remnant of the Noldor.