Best MORTAL fighter

[Numenorean]

Boromir88 -

Don't know about Elendil or Isildur great leaders but as of fighting I don't know enough info on them to judge.

Elendil was a great leader and fighter. He fought and led at the Battle of Dagorlad - a huge, bloody and hardfought clash in which both sides suffered very heavy losses. Elendil then laid siege to Barad-dûr for seven hard years during which there were many more fatalities, including Anárion his youngest son. Elendil (with Gil-galad) eventually faced, fought and overpowered Sauron himself - in a far longer and nastier fight than the movie prologue version.
For the most fell of all mortal warriors I believe Lindil is spot on with this statement:

Turin was a sort of Aragorn gone amok ...Trainied in the 'school' of the marches of Doriath in post-Nirnaeth Beleriand, alongside Beleg for years, this is pretty serious stuff

As mortal fighters go, Hurin Thalion was a complete hero and perhaps even mightier than his son, though maybe not quite so fell as the seventy Trolls he slew at the Nirnaeth were under orders to take him alive.
Aside from his Silmaril heroics, Beren Erchamion fought a near one man guerilla war for over 4 years in Dorthonion after the Bragollach. Beren caused so much damage to Morgoths forces that an entire army was sent to take him out - under the command of no-one less than Sauron/Gorthaur himself, and they failed.