Johann Sebastian Bach
Ludwig van Beethoven
Glenn Gould playing Bach's work was better than Bach himself though. The work itself; the musical notes were perfectly written though.
Beethoven is a bit over-rated with the 'Being deaf and still composing' situation. He kind of cheated his way out of that one, cutting the stands of the piano down to the floor so he can put his ear on the ground and listen to the vibrations. Bach was able to compose genius works that everyone was fairly surprised by at the time, while still abiding to the rules. As Baroque is very strict with rules, he might have broke some but for a purpose that inspired many artists to come.
He was deaf & still wrote excellent pieces.