Achebe's criticisms

Afternoon.

I'm writing a piece of A2 English coursework entitled - "The main protagonists in Heart of Darkness and Waiting for the Barbairians are presented in an unconventional manner. How far do you agree?

My writings on Marlow hinge around his own feelings of being an unconventional agent of empire, however digging deeper he fits in very well with the conventional view. This is a view that Achebe writes about during criticisms. I have scanned what i can find on Achebe's critiques but can't find one or two quotes that sum this view up concisely. Could anyone point me in the right direction?

Many thanks