i think this chap qualifies as ujustly neglected, especially considering his early fame/popularity vs relative current obscurity
Stanchinsky
Hailed as a genius by Alexandrov, Medtner, Prokofiev, and Lourié, Alexei Stanchinsky (1888-1914) was once a household name to Russian composers in the early 20th-century only to be forgotten after the 1917 revolution. Today he is usually regarded as an eccentric composer whose premature death is shrouded in mystery. Throughout his youth, Stanchinsky was prone to mental illness, spent a year (1908-09) in an institution, and was pronounced "incurably insane." He often destroyed his own compositions in fits of hallucination and rage; thankfully, friends and colleagues did much to reconstruct many of his manuscripts. Despite his degrading mental health, Stanchinsky had ambitions in music and concertized widely. Yet in 1914 Stanchinsky's body was discovered near a creek and although the cause of death was unknown, rumors spread that it was suicide. During his studies at the Moscow Conservatory around 1909, Stanchinsky wrote experimental piano pieces that were considered avant-garde for the day. He assimilated elements of Scriabin, Medtner, Mussorgsky, and folk music in the creation of his own style, one that cradles the harmonic language of high Romanticism, especially Scriabin, and his own fascination with polyphonic textures. Interestingly, scholar Larry Sitsky calls Stanchinsky the "Diatonic Webern" for his propensity for diatonic saturation and employment of "polyphony not as a contrasting episode but rather as the essential and organic tool of his music."