Estrangement and "othering" involving race, ethnicity, cultural, and gender divisions have led humans to dehumanize each other and commit great abuses throughout history. Solomon Northup’s account of kidnap, abuse, exploitation, violence, and brutality gives us a firsthand account of the fragility of our ideas of right, equality, and justice. Systems created for the abuse of one group also affect those enforcing this system. The superior and inferior mutually view each other as uncivilized. Using Twelve Years a Slave, analyze how the system of bondage dehumanized and brutalized not only slaves but also those that made a living from the slave economy. How did this mutual "othering" perpetuate and reinforce brutal dehumanization?

Because the prompt asks you to focus on how slavery’s brutality dehumanizes both the slave and the slave owner/seller/controller, I would focus on chapters 12–20 of 12 Years a Slave.  Those are the chapters that cover the ten years that Solomon Northup lives under the tyranny of Edwin Epps.  Edwin Epps is a “nigger breaker,” and Northup is sold to him because of the hatred that Tibeats harbors for Northup.  During those ten years, readers witness the abuse, humiliation, and deprivation that Epps forces upon his slaves.  Epps is able to treat the slaves this way because he simply doesn’t see them as people.  The slaves are property to him.  They are equivalent to tools that are beat on for a purpose and thrown away after breaking.  It’s easy to see how the slaves are dehumanized in this kind of situation; however, Epps is a dehumanized character as well.  The slaves don’t really consider Epps a human because of how inhumane he acts toward the slaves under his control.  Even other slave owners don’t necessarily see Epps as a person.  They see him as a tool to be used to correct deviant slaves.  That’s why he’s known as a “nigger breaker.”  
For a different text that portrays a similar situation to Northup’s experience with Epps, I would choose Narrative of the Life of Frederick Douglass.  Within that text, I would focus on chapters 9 and 10.  Chapter 9 focuses on Douglass’s time with Master Thomas.  After 9 months, Thomas decides that Douglass is too unruly to keep around.  Thomas decides to “lend” Douglass to Edward Covey for one year.  That’s when chapter 10 starts.  
Covey is a well-known slave breaker.  He is considered the best in the area, and Thomas believes that Covey can “train” Douglass to be a better slave.  

Some slaveholders thought it not much loss to allow Mr. Covey to have their slaves one year, for the sake of the training to which they were subjected, without any other compensation.

Like Epps, Covey’s training methods are far from kind.  He mercilessly beats his slaves until they do as they are told no matter what.  Douglass is at first unfamiliar with the tasks that Covey gives him because Douglass is more of a city slave; therefore, Douglass makes simple mistakes.  Instead of teaching Douglass the correct method of doing something, Covey just beats him.  

I lived with Mr. Covey one year. During the first six months of that year, scarce a week passed without his whipping me. I was seldom free from a sore back. My awkwardness was almost always his excuse for whipping me.

Douglass escapes one night, and he returns to Thomas.  Douglass begs for Thomas to do something about the beatings, but Thomas just sends him back.  Thomas does not want to be seen as a man that goes back on a business deal.  

Master Thomas ridiculed the idea that there was any danger of Mr. Covey’s killing me, and said that he knew Mr. Covey; that he was a good man, and that he could not think of taking me from him; that, should he do so, he would lose the whole year’s wages; that I belonged to Mr. Covey for one year....

The conflict in these two chapters shows readers exactly how dehumanizing and brutal the institution of slavery is.  Slaves were regarded as property, not people; therefore, men like Douglass could be bought, sold, traded, and loaned like any other piece of property.  Both Covey and Epps have the opinion that slaves are not people with feelings.  If they did think that, then they wouldn’t repeatedly beat the slaves nearly to death.  I think the fact that Thomas doesn’t take Douglass back is also incredibly important regarding the dehumanizing aspects of slavery.  Thomas can easily see that Douglass has been severely beaten, yet Thomas refuses to go back on his original business deal with Covey.  Douglass is not a human to Thomas.  Douglass is a material good, a commodity, and Covey is supposed to be the kind of person that can make Douglass a more valuable commodity.  Even if Thomas wanted to help Douglass, the institution of slavery has made it more profitable for him to ignore what is happening to Douglass.