Like any hero he is not afraid of challenging people who are far superior to himself. He shows his courage and strength when he fights the great Lord Voldemort alone.
Dumbledore is the greatest and most wizard. He is extremely protective of Harry and there is not an ounce of evil contained within Dumbledore. He is also very powerful, but in a controlled way and uses his power for good only. He is like a guide in Harry's life and leads Harry to making the right decision. He is almost like a guardian angel that watches over Harry and insures his security, "as long as Dumbledore is there, Voldemort can't touch you. You are safe when Dumbledore is here." The reason for Harry being safe when Dumbledore is around is because he is the one wizard that Voldemort has always feared. The purpose of Voldemort fearing Dumbledore is he is less powerful, but strives to have Dumbledore's power.
There is an immediate contrast to do with power between Dumbledore, the leader of the good side and Voldemort, the leader of the bad side. This is because Voldemort wants to use his power to conquer and do evil, and Dumbledore uses it in a controlled good way. An example would be the Philosophers Stone. On one side it is used for keeping someone alive, who is Nicolas Flamel and on the other it is used for power and invincibility, which is what Voldemort wants the stone for.
There are different types of evil. Voldemort represents a serious evil, which is willing to kill people to gain power, but Draco Malfoy is a minor evil who is more unkind and horrible, than downright evil.
Malfoy is Harry's enemy at school. Malfoy is an arrogant, middle class boy who likes to boast about his father's wealth. He comes from a privileged background and is therefore spoilt. Because of this he looks down to people, "red hair, banged up wand, dirty robes, it's obvious you are a Weasley." This is Malfoy bullying Ron because of his class and difference to Malfoy.