Biff does sometimes makes mistakes like his father does, but he usually tries his best not to. Because of his upbringing, in which Willy taught him it was fine for him to take and use things that don’t belong to him, when Biff’s interview with Bill Oliver goes badly wrong, not really even ever taking place, he becomes angry, and in his anger he takes Oliver’s fountain pen. This incident proves that the lies Biff was fed during his childhood still sometimes affects his behaviour almost twenty years later. This is one of the few cases where Biff does anything particularly bad, but this is caused mainly by his upbringing as opposed to being his own choice.
Most of the time though, it’s hard not to sympathise with Biff. The most horrifying experience for him obviously must have been when he went up to Boston to see his father, and finds him with the woman. This betrayal completely crushes Biff. In the space of just a few short seconds, he finds out that his father, the man he admired and loved more than anyone else in the world, is a cheat, that he has lied to Biff for his entire life, and that his father is nobody special, and certainly is not the amazing salesman that he claims to be. The other reason the experience is so traumatising for Biff is the guilt he must have felt afterwards: he