UNITARIANS CONSIDER HIM A MARTYR:Michael Servetus - Wiki

"
Because of his rejection of the Trinity and eventual
execution by burning for heresy , Unitarians often
regard Servetus as the first (modern) Unitarian martyr
—though he was a Unitarian in neither the 17th-
century sense of the term nor the contemporary sense.
Sharply critical though he was of the orthodox
formulation of the trinity, Servetus is better described
as a highly unorthodox trinitarian.[50]..."

https://en.m.wikipedia.org/wiki/Michael_Servetus