In the original novel, and across multiple media platforms over the last two hundred years—theatrical or cinematic adaptations involving many diverse character interpretations—the creature has generally been portrayed as the seminal “Sympathetic Monster,” or, in contemporary terms, an anti-hero. There are any number of justifications for that in the novel itself, but it’s actually relevant in this instance to reference the subsequent hundreds of film adaptations and derivations of the germinal idea, revealing of the Monster’s character and temperament.
Who is the Monster? Does he get to have body parts, an education, or security of his own? What does it do to you to be routinely ostracized and outcast? Frankenstein’s Monster is like an onion with many layers: to really know about him, you have to use the novel (the core text) as your point of reference. There are are a billion other artifacts (Frankensteiniana!) that are instructive, but they’re distractions. The film adaptations do, however, focus, synthesize, and refine preexisting narrative elements, and thus impose a brutal clarity upon the substance of the novel.
The Monster is an outsider and a martyr, and, as far as his capacity for evil, it’s (relatively) understandable when each of his provocations and sufferings is accounted. This is in contrast to the intellectual and emotional shallowness of his creator, Victor Frankenstein, who is so consumed with shock and denial, at least at first, to accept responsibility for the Creature and his trauma.
So, overall, the takeaway about the monster is that he’s so wretched and oppressed by his circumstances and struggles—and having to shrug off the sins of others—that it would be fundamentally inhumane to not sympathize with him, particularly during his first-person passages.