Although the world of Harry Potter is almost exclusively focused on the world of wizards, witches, and magic, there are a few human characters splashed throughout JK Rowling's stories. These humans, more commonly referred to as muggles or no-majs, do often play a key role within the tales, despite their lack of magical power and their exclusion from the wizarding world.
Frankly, most of the muggle characters in the stories are at best jerks, and at worst truly evil, but there are a few decent humans that make their way into the story as well. These are all of the major muggle characters, ranked from most heroic to most villainous.
Jacob Kowalski
Clearly, as far as heroic muggles go, there is really no competition for Jacob Kowalski. He is such a genuine and sweet man who is completely ride or die for Newt, Queenie, and pretty much everyone he befriends, and he's one of the few muggles that actually deserves to be a part of the wizarding world.
He rolls with every strange punch that comes his way, and it's easy to see why everyone around him seems to instantly love him.
Hermione Granger's Parents
While Hermione's parents get barely any screen time, their goodness seems to shine through in the fact that they raised such a wonderful daughter.
They may just be average dentists, but Hermione became one of the most powerful and courageous witches in the wizarding world, and the fact that she erased herself from her parents' memories just so she could go off and fight Voldemort without putting them in danger is a testament to what kind of people the Grangers must be.
Dudley Dursley
For most of his appearances within the canonical series, Dudley Dursley was a veritable nightmare of a child.
However, he did manage to redeem himself at the last gasp, and it seems obvious that a lot of his worst attitudes and behaviors stemmed from the fact that he was the horrifically spoiled son of two even more terrible muggles. His relationship with Harry later in life did show that Dudley was capable of a lot of growth.
Marjorie Dursley
Clearly Harry Potter author JK Rowling does not have a very high opinion of people, given that the vast majority of muggles that appear in the series are horrendous, cruel bullies.
Aunt Marge is unsurprisingly in line with most of the terrible muggle characters in the series, and is only saved by the fact that she makes one appearance in the story. She's memorable for all the wrong reasons though, and the world would have been a better place had she just floated away into nothing.
Tom Riddle Sr.
It's fair to say that Tom Riddle Sr. was a muggle victim of the wizarding world, however, he didn't seem to be a very good person either.
It's understandable that he freaked out once he came out of his love spell-induced fog, but the fact that he didn't hesitate to abandon his own son who was completely innocent in the situation clearly shows that he was a pretty awful person in his own right.
Tobias Snape
While the audience is only ever given information about Tobias Snape via Severus' memories, nothing that is ever revealed about him is good, and it's actually a lot easier to sympathize with Severus after realizing that his father was neglectful and abusive.
Tobias mistreated his witch wife Eileen and his son as well, and it comes as no surprise that Severus had such trouble socializing and forming attachments with people given his father's treatment of him.
Vernon Dursley
It takes a special kind of jerk to abuse and torment a child left in their care while doting on their flesh and blood son, but that is exactly what Vernon Dursley did.
It's a borderline miracle that Harry Potter turned out so well despite having a father figure like Vernon, and Vernon is such a spiteful meanie that he clearly genuinely wished that Harry would have had a terrible and lonely life forever.
Petunia Dursley
Petunia and Vernon are truly a perfect match made in hell, but what makes Aunt Petunia ever so slightly more awful than her husband is that Harry is her blood nephew.
Clearly Petunia was miserably jealous of her sister, but to take that out on her orphan nephew for his entire life is truly a special kind of cruel. She deserved a lot more than a good hollering howler from Dumbledore.
Chastity Barebone
Obviously children are the product of their environment on some level, so Chastity Barebone can't be blamed entirely for her nightmarish behavior.
However, while she may not have become an anti-magic activist without the push from her mother, she clearly went whole hog into the movement, and participated in a lot of cruel and abusive behavior as a result of her anti-witchcraft ideology.
Mary Lou Barebone
When it comes to awful muggles in the wizarding world, it would be pretty hard to top Mary Lou Barebone.
Her zealous hatred of all things magical was not only dangerous to the world at large, it led her to horrifically abuse her own adopted children to the point where Credence developed an Obscurus. It's terrible, but the fact that Mary Lou was destroyed by her own prejudices does seem somewhat just.