Samuel Vimes
In Men at Arms, Captain Vimes has to train a dwarf, a female werewolf and a troll to become police and he trains Carrot Ironfounderson to take over as captain of the Night Watch when he retires and in the end Lord Havelock Vetinari is impressed enough that he decides to put Vimes in charge of all the police to fight against corruption and has Vimes start to call himself Commander Vimes.