Although his long line of victims might suggest otherwise, The Expanse's Amos Burton isn't a sociopath, and his personality is actually the result of an as-yet-unseen backstory. Widely hailed as the best science fiction series on TV, The Expanse's leading figures are a well-rounded, fascinating and multi-faceted bunch, all harboring a shady past that the audience has not yet fully unearthed. Perhaps the most complex of the Rocinante crew is Amos Burton, played on TV by Wes Chatham, who pulls double-duty as the ship's engineer and its muscle; fixing the ship and then beating up the people who damaged it.
Those who cross Amos often characterize him as a monster - a violent, fierce and short-fused golem who punches first and asks questions later, devoid of all emotion. Although Amos' raw physical strength has bailed the Rocinante crew out of many a scrape, his brutality has also drawn fear and scorn from those around him, leading to accusations (both on-screen and off) that Amos is some kind of sociopath, hurting people and lacking the empathy to understand why he's in the wrong. While there is plenty of (bloody) evidence to back-up this character assessment, to dismiss Amos as a sociopath does the character a disservice.
Although it's not always obvious, Amos does have a moral compass - it just doesn't point to the same poles as everyone else's. Amos' close friendship with Naomi partly comes from requiring a guide to help make the right choices in ethical situations. The fact that Amos recognizes his need for assistance proves he isn't a sociopath in the traditional sense, and highlights how, despite his internal wiring, Amos is trying desperately to be a better person. This point is reinforced in The Expanse season 2 when Amos is interrogating a Protomolecule scientist called Cortazar, who had his empathy artificially removed, and hopefully asks if a reverse of that process could be possible. Amos resolves to surround himself with good people who have the emotional capacity and knowledge he lacks, such as Naomi and James Holden, while regularly attached himself to a certain cause, usually a frightened child in need of help.
While these actions prove that Amos isn't a sociopath in the stereotypical fictional sense of the word, it remains clear that something is wrong with him. Amos expresses some symptoms of a sociopath-esque personality disorder, such as the lack of empathy and outbursts of calm violence that go beyond what's necessary in the situation. However, Amos also shows signs of PTSD (post-traumatic stress disorder), with a sense of unpredictability, disassociation and a habit of being triggered by some distressing situations more than others. Additionally, a fascinating blog post from almostdefinitelydying argues that The Expanse's Amos is actually autistic. Certainly, his keen strategic sense, methodical way of thinking (he's an expert engineer) and difficulty in social situations fit far better with this diagnosis than that of a sociopath.
More than your average violent TV "psycho," Amos is a melting pot of mental problems and disorders, accumulating more damage during his lifetime than the Rocinante he works so diligently to fix, and his childhood is likely to blame for this. On TV, The Expanse has barely touched the surface of Amos' past, but James S.A. Corey's The Churn and Nemesis Games help flesh-out the character's tragic backstory. Inducted into crime at an early age and sleeping with his foster mother, Amos was originally called Timothy, and worked for a mob boss by the name of "Amos Burton." Timothy killed Amos in order to protect a close friend, and subsequently assumed his victim's identity, going by that name ever since.
Given that he clearly suffered a great deal in childhood (there's even allusions towards prostitution), it's no surprise that Amos suffers as an adult, and his disposition to help abandoned youngsters betrays the fact that his childhood is the root cause of his cracked psyche. Amos sees himself as the scared, lonely children he's so often trying to help. It's also interesting that while the Rocinante has finally provided Amos with a true home, the crew do sometimes take advantage of his usefulness and unerring trust in them. Whether Amos' history is explored in The Expanse season 5 remains to be seen, but the character is certainly much more than a run-of-the-mill thug with anger issues.
The Expanse season 5 is currently without a release date.