I don't think anyone has yet mentioned the badasses from the Malazan books, so I will throw in these three-
Dassem Ultor
Karsa Orlong
Icarium
You forgot the most ridiculous of all Malazan warriors, Anomander Rake, who is what would happen if you got a 14-year-old to eat a whole bucket of halloween candy and then try and come up with "A BETTER ELRIC".
Details (in all caps because that's kind of how I feel the author thought of them in whatever D&D/GURPS campaign Anomander is from):
ANOMANDER RAKE IS A COOL DROW NOT A LAME MELNIBONEAN
ANOMANDER RAKE IS SEVEN FEET TALL
ANOMANDER RAKE IS BUILT LIKE A WWE WRESTLER NOT AN UNHEALTHY WIMP
ANOMANDER RAKE ALSO HAS A SWORD THAT EATS SOULS BUT ITS WAY BIGGER THAN STORMBRINGER AND WAY MORE POWERFUL
ANOMANDER RAKE HAS A WHOLE ASS FLYING CASTLE NOT A LAME EARTH BOAT
ANOMANDER RAKE CAN TURN INTO A DRAGON AND ITS WAY TOUGHER AND BIGGER THAN OTHER DRAGONS
ANOMANDER RAKE IS ALSO A SUPER POWERFUL WIZARD NOT A WEAKSAUCE ONE LIKE LAME ELRIC
And that's kind of the tip of the iceberg.
Most of the best fantasy and mythological warriors have already been discussed, but I always liked Ash from the Book of Ash series by Mary Gentle. Continuing the "obscure books" theme, I really liked Asmander and Venat from Adrian Tchaikovsky's least-read series, Echoes of the Fall, about shapeshifters involved in series of fairly desperate wars. I don't think any of them are top-tier but they're pretty cool.
I'm excluding assassins because I could list a lot of extremely cool assassins, but I feel like that's a different genre (and pretty much rules out 90% of Unhewn Throne characters for example).