I feel much of this comes down to a matter of preference and speculation, but I went with my gut and based on my limited knowledge, I voted for
Fingon. He was known for his valor and skill in battle, and there was much proof of this in his deeds throughout the
battles he participated in until his death. He may have lost in combat against Gothmog, but he was essentially ganged up on by two
balrogs, and this happened in the middle of the bloody chaos of
Nirnaeth Arnoediad, where his kinsmen were being slaughtered left and right. I like to believe at least Fingon went down fighting as hard as he could, trying to save as much of his people as he can (a heroism he demonstrated when he rescued
Maedhros).
I personally refuse to even consider giving "best warrior" to the kinslayers/child killers who mowed down innocent people all for an oath to their villainous father. They can compete for "best murderers". (See my angst! 🤣)
I would also like to say that if we would base judgement on who survived longest, then
Galadriel would obviously win. However, I don't believe I've ever found any proof of her actually fighting in any of the great battles of the
First Age, and almost feel like she's the Waldo of the group. ("Where's Galadriel??") In fact, if anyone can explain to me exactly but concisely where Galadriel was during the
wars (aside from residing in
Doriath for a nonspecific time before migrating eastward with/without
Celeborn), I would genuinely appreciate it. 😁