On the surface, Sunday is an excellent leader: He seems reasonable, hardworking, an absolute moral model to outsiders, and a natural leader and judge. In the face of (what Sunday considers) virtue, he will offer unconditional acceptance with a big heart. In the face of evil, he will rain down merciless punishment.

On the inside, Sunday is not nearly as kindhearted as he seems. A control freak by nature, he takes pleasure in controlling the behavior and thoughts of others, which is how he became a Family spokesperson. He will coerce, discipline, and even punish others with great effectiveness in order to satisfy his own selfish desires. ( This is not directly shown in the story ) 

Be that as it may, Sunday is not an absolute hypocrite: His great empathy and compassion are real, and he is thus able to guide the public and indeed lead The Family and Penacony upwards for many an Amber Age. He will heartily rejoice in the joys of others and grieve over their sorrows — but that doesn't stop him from fulfilling his selfish desires with a strong hand.