Why did the Radical Republicans oppose Lincoln's Ten Percent Plan?

Republicans opposed this because they thought Lincoln's plan was too mild. They argued that the congress, not the president, should control Reconstruction policy. Their plan was called the Wade-Davis Plan. In the Wade-Davis plan 50 percent had to swear loyalty and if you were a Confederate you would not get to vote.

Explanation:

It was when 10 percent of the voters of a state took an oath of loyalty, to the Union the state could form a new government and adopt a new constitution - a constitution banning slavery.