I'd probably go Feanor.

Glorfindel

I'd say Gil-galad: he helped kill Sauron, and was the High King of the greatest Elven Kingdom.

I think maybe Fingolfin? since he was the last one to fight in single combat with Morgoth...

Definitely not Gil-Galad. Probably Fëanor with Fingolfin a close second. Eärendil killed Ancalagon the Black, but not by himself.

Fëanor fought at least two Balrogs plus other forces of Morgoth probably by himself. Fingolfin fought Morgoth one-on-one. Ecthelion of Gondolin who slew Gothmog and Glorfindel who also slew a Balrog are high on the list.

Tolkien explicitly called Fëanor the most powerful Elf.

Only Fingolfin and Galadriel were match to him.

And Galadriel?? What is your source on that? You've been watching the movies too much.

@WizardWarrior1

In The Shibboleth of Fëanor, the following words are said:

"Galadriel was the greatest of the Ñoldor, except Fëanor maybe, though she was wiser than he, and her wisdom increased with the long years."