Remus Lupin

Appearance
In the books, Lupin appears significantly older than his years due to constant painful transformations and a difficult life:
Face and Hair: He has a pale face with premature wrinkles and light brown hair that has turned grey early.
Scars: His face and body show signs of deep scratches from his transformations (in the films, this is emphasized by thin scars across the bridge of his nose and cheeks).
Clothing: Remus always looks poor and unkempt. His robes are threadbare, patched, and baggy. This is a consequence of his lycanthropy making it extremely difficult for him to find steady work.
Overall impression: He looks exhausted and sickly, but his gaze remains kind and insightful.
Character
Lupin is one of the most humane and wise heroes of the saga.
Peacemaker: Unlike the brash Sirius and James, Remus has always been the voice of reason. He's gentle, calm, and reasonable.
Humility and insecurities: Because of his werewolf status, he considered himself "unworthy" of love and friendship. This created a deep insecurity within him: he long rejected Tonks's feelings, afraid of ruining her life.
Teaching Talent: He is a brilliant teacher. Remus has a rare gift for connecting with every student, encouraging the weak (remember his support for Neville), and explaining complex concepts in simple terms.
Loyalty and Guilt: He is infinitely loyal to his friends, but has reproached himself all his life for not always being able to stop their cruel antics towards Snape during his school years.
Toughness: Despite his soft exterior, Lupin is a brave fighter of the Order of the Phoenix, willing to sacrifice himself for the greater good.