What is the most accomplished piano solo piece?

There is no definitive answer to this question, as it is a matter of personal opinion. However, some piano solo pieces that are widely considered to be among the most accomplished include:

* Bach's Goldberg Variations

* Beethoven's Piano Sonata No. 14 ("Moonlight Sonata")

* Chopin's Études, Op. 10 and Op. 25

* Liszt's Transcendental Études

* Rachmaninoff's Piano Concerto No. 3

* Prokofiev's Piano Concerto No. 3

* Stravinsky's Three Movements from Petrushka

These pieces are all technically demanding and require a high level of virtuosity to perform. They also display a wide range of musical styles and techniques, from Baroque counterpoint to Romantic lyricism to modernist atonality.

Ultimately, the most accomplished piano solo piece is the one that an individual performer feels the most connected to and inspired by.