Most powerful in ME

[the phantom]

Here are my picks-

First Age:
bad- Melkor
good- Feanor

Second Age:
bad- Sauron
good- Elrond

Third Age:
bad- Sauron
good- Gandalf

It's difficult to pick the most powerful mainly because Tolkien rarely said "this guy was more powerful than this guy". He called individuals the "greatest", but as The Barrow-Wight humorously pointed out in another thread, according to his dictionary if someone is called the greatest then it means they are the largest.

We don't know exactly what Tolkien meant when he said "greatest". What particular virtues and abilities have more to do with greatness in his mind? Does he subtract points from bad individual's total greatness points because they are bad and he considered good to be greater? Does he disregard some things that we wouldn't and consider things we wouldn't?

So not only are all of those "greatest quotes" (as I like to call them) ambiguous, but also remember- greater does not mean more powerful (and "most powerful" is what the thread title says). Try finding more specific quotes than "so and so was the greatest". For instance, from the Sil-

For Feanor was made the mightiest in all parts of body and mind, in valour, in endurance, in strength and in subtlety alike, of all the Children of Iluvatar, and a bright flame was in him. The works of wonder for the glory of Arda that he might otherwise have wrought only Manwe might in some measure conceive.

That's what I call specific praise of a powerful person.