Frank Hunter is self-confident, successful, personable, friendly, yet with enough arrogance about him to engage in an extra-marital affair with the wife of his colleague, Dr. Crocker-Harris. Students find it easy to talk with Hunter and to confide in him, as John Taplow confides in him while waiting for Crocker-Harris. Hunter knows just the right thing to do socially to make other people feel at ease and receptive, as is illustrated by his impromptu instruction on golf swing while Taplow waits for Crocker-Harris.
In contrast, Andrew Crocker-Harris is ill at ease with himself and others and is viewed by himself and others as a failure in his teaching career mostly because, as Taplow puts it, he is unable to pass on his love of Classical literature to his students. While students admire Hunter, they ridicule and tease Crocker-Harris calling him, among other things, "Himmler of the lower fifth."
The most interesting characteristic about Hunter is that, while his attentions to Millie Crocker-Harris were strictly for physical pleasure, he is finally able to see the nobility within the disappointed Crocker-Harris, who even had his pension voted away from him. This insight is expressed in Hunter's advocacy of the genuine nature of Taplow's gift and of his confession to Crocker-Harris of his affair with Millie.
The most interesting characteristic about Crocker-Harris is that, while he has every reason for bitterness, resentment and anger, he remains humble and accepts, with grace and dignity, the sincerity of Taplow's gift and Hunter's proposed visit.