During the Indian freedom struggle, it was Subhash Chandra Bose who formed the party called `Forward Bloc`. Subhash Chandra Bose was a prominent leader in the Indian National Congress and had differences with its leadership. He believed in radical methods to achieve independence and broke away from the Congress to form his own party, the Forward Bloc, in 1939.

Option 1: C. R. Das was an important freedom fighter and a member of the Indian National Congress, but he did not form the Forward Bloc.

Option 2: M. N. Roy was a political activist and a co-founder of the Communist Party of India. He did not form the Forward Bloc.

Option 3: Rash Behari Bose was a revolutionary and a key figure in the Indian independence movement, but he did not form the Forward Bloc.

Therefore, the correct answer is option 4, Subhash Chandra Bose.