Do you see any positivity in Night that foreshadows Wiesel's willingness to fight for peace, or did he turn cruel during his experience?

The "positivity" in Night is seen in Eliezer's sensitivity to human suffering.

There is much in Night that can foreshadow Wiesel's future commitment to human rights.  Throughout Night, Eliezer shows a high level of sensitivity to the pain that people experience.  As a result, we see someone who pays attention to the cries of human suffering, something that Elie Wiesel did throughout his adult life.

Eliezer pays very close attention to how people suffer in Night.  He is direct in describing how Moshe the Beadle wept because no one listened to him. He is pointed in recreating the night that Madame Schachter was beaten on the train because she kept on screaming that she saw "fire."  In both of these situations, Eliezer pays attention to how people suffer and the indifferent reactions others have to such pain.

When Eliezer enters Auschwitz-Birkenau, he is aware of what he sees around him.  In the poem, "Never Shall I Forget," Eliezer bears witness to his first night in the camp.  His sensitivity to what he experienced can be seen in lines such as "Never shall I forget the small faces of the children whose bodies I saw transformed into smoke under a silent sky" and "Never shall I forget those moments that murdered my God and my soul and turned my dreams to ashes."  Eliezer's attention to how human cruelty can personally transform the the individual is another example of how he displays a sensitivity.  It is a quality that foreshadows the advocacy that was so much a part of his adult life.

Eliezer's sensitivity to life in the camps prevents him from being indifferent. He displays this when he talks about the hanging of a five year old boy or in how Rabbi Eliahu's son betrayed his father.  When he speaks of how people forgot to recite the Kaddish for Akiba Drumer or when he details how the son lied about his father so he could steal his bread, Eliezer speaks for those who lost their voices because of Nazi cruelty.  Eliezer applies this to himself when he speaks of his father's death:  "No prayers were said over his tomb. No candle lit in his memory. His last word had been my name. He had called out to me and I had not answered."  Eliezer displays a wide scope of emotional understanding.  Through his example, morally acceptable behavior is rooted in an insistence on speaking for as many voices as possible and accepting responsibility when that standard is not reached.  This is a part of the narrative that foreshadowed what he would do once he left the camps.

Eliezer is not cruel in Night.  He does not take the form of the barbarism around him.  It is very difficult to suggest that his drive for survival makes him a bad person. Rather, in Night, we see that Eliezer pays attention to the pain that other people experience.  He displays a heightened sense of care towards other peoples' narratives.  He recognizes that validation of voice is the only way one can counter a reality based upon the exertion of cruelty and infliction of human suffering. These qualities foreshadow the man that Eliezer would become, a towering paragon of defending and preserving human rights around the world.