The debate between the disciples of Kant started in the late 1780s, while Kant was in his prime—at times, Kant himself vigorously argued with his disciples. I think, Hegel is only other figure in western philosophy whose work has led to such intense controversy as Kant’s.
Here’s a short exchange between the two dedicated Kantians—Reinhold and Maimon:
"All philosophy must begin with self-evident facts, and these are indemonstrable since they are the basis of all demonstration.” ~ Karl Leonhard Reinhold in a letter to Salomon Maimon (1791)
"Of course all philosophy must begin with self-evident facts, but the question is how we know the principle of consciousness expresses such a fact.” ~ Salomon Maimon in his reply to Karl Leonhard Reinhold (1791)