Who is Gavril Ardalyonovich Ivolgin from The Idiot and what is their importance?

Dostoevsky initially presents Ganja as a scoundrel. He wants to marry Anatasia Filippovna purely for financial reasons and hits his own sister when she questions his decision. In fact, he runs his household, which includes his own father, with an iron fist. However, as the novel moves on, Dostoevsky shows these characteristics as mere pretense and when Ganja does have the opportunity to prove he is a real scoundrel, he cannot go through with it. Dostoevsky shows this when Anatasia Filippovna throws 100,000 roubles into the fire. Instead of taking it out, Ganja stares at the money, eventually fainting. Even when Anatasia leaves the money by his unconscious body, he later gives it back. His relationship with Prince Myshkin is also like this. Initially he calls the Prince an Idiot and a gossip and at one point slaps him in the face. However, when the Prince is having problems with Burdovsky, Ganja steps in and resolves the situation.