Perhaps the canonical example is Nikolai Ivanovich Lobachevsky? His work on hyperbolic geometry was subject to severe ridicule, stemming from a negative review of Ostrogradsky, the leading Russian mathematician of the time. Perhaps the severity of the ridicule piled on Lobachevsky was part of the inspiration for Tom Lehrer's song Lobachevsky?

Needless to say, Lobachevsky's work became widely accepted later.