Brass

Brash

No, I mean brass: “figurative. Taken as a type of insensibility to shame: hence, Effrontery, impudence, unblushingness.” (DEFINED)

Brash would not have been appropriate (defined as “self-assertive in a rude, noisy, or overbearing way”). Tim was not rude, noisy or overbearing, but he was absolutely shameless!