Having studied them somewhat in depth, I have to say Mozart and Beethoven.
Mozart had two very rare abilities: a photographic memory and perfect pitch. Once, when he was 5 years old, he went with his family to church, where he heard a mass that he really liked. When he got home he sat down, after hearing the mass only once, and wrote it down note for note. That's all the choir parts and the soli. I don't know if you've ever tried taking musical dictation, but to write a
single melodic line takes most skilled people 2 or 3 times to write. That's for one little 5-second snippet of a melody. This guy wrote down at least 20 minutes of music in full counterpoint.
Beethoven may not have had the natural genius that Mozart had, but he knew how to arrange music in ways that turned simple notes into masterpieces. Take a look at the ninth symphony. He takes his idea of brotherly love of mankind and turns it into what is possibly the greatest work ever written.
Other notable mentions in this category are Bach, who basically redefined counterpoint; Wagner, who redefined the opera, and Ockeghem, whose
Missa Prolationum with its technical complexity continues to astonish composers more than 500 years after it was written.
I would also advise you against giving lechepicha any new thread ideas.
The name STBNW comes to mind...