Atrocities and cruel treatment can make good people into brutes. Does Elie himself escape this fate?

In many circumstances where a person is treated cruelly, this person becomes cruel themselves. In the case of Elie Wiesel, the author of Night, Elie does not become a cruel person.
The novel Night is Weisel's story about the time he spent in concentration camps during World War II. During this time, Wiesel saw many horrible things, such as the hanging of a small child. In addition to the horrible things that were done to the prisoners by the soldiers, there were many acts of violence and rebellion that the prisoners committed in an attempt to gain back their humanity. During this time, Wiesel did not participate in any of these acts, which shows that he did not become a brute (or a violent person).
Wiesel, after surviving the concentration camps, started the Elie Wiesel Foundation for Humanity, helped start the building of the Holocaust Museum in Washington DC, and also won a Nobel Peace Prize. Wiesel, rather than focusing on his anger and becoming violent and vengeful, used his experiences to put effort into making the world a better place.

In my opinion, the answer is yes, Elie Wiesel does escape the fate of turning into a brute.
His book, Night, is an autobiography of his time in German concentration camps during World War II. He describes horrible acts of violence done to people by the Nazi soldiers, as well as heinous acts of inhumanity committed both by soldiers and prisoners. He doesn't participate in the violence and maintains his conscience and his humanity. He is angry, understandably so, and directs much of his anger toward God, which may be what allows him to escape the fate of becoming a brute. It's my belief that most people who abuse others after having been abused are filled with anger and direct that anger toward other humans. Elie doesn't do this; he accuses God and releases all his anger toward him. Elie Wiesel won the Nobel Peace Prize in 1986 for Night. The Norwegian Nobel Committee called him a "spiritual leader" and a "messenger to mankind" promoting peace, atonement, and human dignity. Below are some quotes from the book Night that support the viewpoint that Wiesel escapes the fate of becoming a brute.

This day I had ceased to plead. I was no longer capable of lamentation. On the contrary, I felt very strong. I was the accuser and God was the accused.

Because of his faith, Elie believed that God could have stopped the German soldiers and their heinous crimes. When he sees that God does not stop it, he loses faith and directs his anger toward his God.
The following quote comes at the end of the book, at the time of Wiesel's liberation. It shows his priorities and thought processes after his rescue from the horror of the concentration camps. Notice that he does not think of revenge. All the anger seems to leave him at the time of his liberation.

Our first act as free men was to throw ourselves onto the provisions. We thought only of that. Not of revenge, not of our families. Nothing but bread. And when we were no longer hungry, there was still no one who thought of revenge. On the following day, some of the young men went to Weimar to get some potatoes and clothes—and to sleep with girls. But of revenge, not a sign.