Even Evil Has Standards: Yeah, he's a bully, but he being the "alpha-bully" he declared the disabled Stevie off-limits for bullies (inlcluding himself, unless Stevie partakes on the abuse of his own volition). In fact, making sure the other bullies respected his standards eventually became his reason to retain his alpha-bully status.
Even when he finally snaps and decides to beat up Stevie because he keeps humiliating him, Reese completely numbs and weakens his own legs to make it a fair fight.
Also, while he makes other nerds do his homework for him, he doesn't want to interfere with their weekends, and apparently protects the nerds who work for him from the other bullies.
Hearing Voices: He has mentioned hearing voices on more than one occasion. One time he told Dewey that the voices are not his friend, and another time he comments about how the voice in his head that tells him to do stupid things was getting quieter.
A good example? After Malcolm give him a book report guaranteed to be an A, his (then) girlfriend, Alison, realizes that she forgot to do hers, lamenting on how she can't afford another F. Reese's solution? Tearing the report in half, insuring that "now [they'll] both get Cs".
Calling The Parents Out: He frequently manages to get revenge against Hal and Lois whenever they neglect him or treat him unfairly. Hal forgot his birthday led to Dewey publicly shaming him in front of every single attendee at a Bridal expo. Lois saying she couldn't get a vital component to a science experiment (which led to Dewey failing) resulted in Dewey Gaslighting her. And for the most part, he actually gets away with it.
Character Development: Undergoes this more than any other character (with the possible exception of Francis). Over the course of the series, he evolves from a ditzy Cloudcuckoolander with an overactive imagination into a Wise Beyond His Years child prodigy who is just as smart as (if not moreso than) Malcolm. Justified, given that he ages through the most critical period of child development during the time course of the series (going from a pre-adolescent child in the pilot to a young teenager in the finale).
Ignored Epiphany: Tried to explain one to Reese and Malcolm in Buseys Run Away. After finally being put in a normal classroom, Dewey lacks the drive to commit heinous pranks with his brothers like he used to. Therefore, he starts bonding with Lois while Malcolm and Reese keep getting punished. They don't understand what's going on, and Dewey tries to explain that the reason Lois is acting so nice to him, is that he hasn't done anything stupid or destructive, so she hasn't needed to punish him. "It's not her, it's us." His brothers didn't get what he was saying and automatically assumed he's become Lois' spy.
The epiphany turns out to be wrong when it turns out Lois is treating him differently only because he managed to move back to the regular class.
Papa Wolf: Dewey will do everything in his power to protect and nurture the kids in the special classroom, because no one else is willing to.
Also to his younger brother, even tricking his own parents to ensure that the younger brother gets the attention from his parents that he himself never got because they were always to busy dealing with their more troublesome kids.
Too Dumb to Live: In a flashback: while one of his brothers is cranking the pedal of an overturned bicycle, he takes a bite out of the spinning wheel. He grows out of this much quicker than his brothers, and starts to take pleasure in hurting and manipulating others instead.
Well-Intentioned Extremist: Was willing to do anything to ensure that his brother got even a decent childhood, even if it meant tricking or humiliating his parents in the process.
Wicked Cultured: Dewey is clearly the second most intelligent member of his family, the most cultured and sophisticated, and arguably the most devious.
Lois realizes it's likely Dewey that was Gas Lighting her because she knew Reese couldn't possibly have kept it a secret for so long and Malcolm didn't have the patience he did.
Calling The Old Lady Out: Frequently rebels and insults Lois, and it is heavily implied that it is for no other reason than just to spite her.
His female equivalent, Frances, is similar, although her hate is more directed towards her dad, blaming him for none of her marriages working out.
Character Development: He becomes a lot more responsible as the series progress. In fact, many later episodes deal with how he fights his insane impulses (like when he warned Reese against collecting toilet rings from a dump like he did as a teen but ended up trying to beat Reese's record.) By the end, he is married and in a stable office job that, unlike Hal, he likes. It's possible though that Hal did like his job when he was the same age as Francis, but grew to resent it.
Cool Big Bro: He's seen this way by Malcolm, Reese and Dewey.
Enfant Terrible: In the episode Lois fights Jamie, in flashback form, we learn that Francis was absolutely horrible as a toddler. Probably the worst act he committed was using the last of the china to pour a flammable substance (lighter fluid) onto his teddy bear, and then set it on fire, which also resulted in Lois becoming the mother she currently is. It's also hinted that Lois's attempt at loving Francis (by placing the already burning teddy bear in the fireplace, burning her hand in the process) was a painful memory for him, given his reaction when he tells Lois this.
Even Evil Has Standards: He refused to fight against his boss, Lavernia, because she is a woman — until she ended up mocking his mother. He then fights back and the fight ended with a draw.
Fourth Date Marriage: He and Piama knew each other a very short time before getting married. Slightly deconstructed when there are several moments where they wonder whether their relationship can work out, but ultimately they remain together.
Never My Fault: He tries to pin (almost) all of his faults on his mother. In fact, he was legitimately stumped when his C.O. told him to think of one thing that he did wrong that he doesn't blame on his mother. The only time he actually did admit to wrongdoing without blaming his mother or anyone else was when he admitted that it was his fault that his brothers turned out the way they did.
In the final season we discover that he's a recovering alcoholic and that he has been blaming Lois for his problems in his AA meetings. Then Piama accidentally reveals that Francis is not a drunk but that he's just using AA to vent and Lois gives him a rare form of a "The Reason You Suck" Speech. She tells him that he needs to grow up and stop blaming his mistakes on her or on the alcohol, and leaves him to take a look at himself in the mirror, which he does... Until he sees Piama in the reflection, then he starts blaming her.
Playing with Fire: This is what causes Lois to attempt to pull a complete 180 on her raising methods (he nearly set his teddy bear on fire, and the fact that he was pouring gasoline on it and then attempting to light it implied that he was doing so deliberately)
Troubling Unchildlike Behaviour: As a toddler, Francis attempted to douse his teddy bear with gasoline and then set it on fire before Lois intervened. Later, as a child, he had locked his parents out of the car while his mom was going into labor, and he also frequently tortured his brothers, stole their toys, locked them in a closet, and at one point scarred Reese with a bayonet.
Enfant Terrible: He's so bad that he actually manages to break his mother's spirit.
Troubling Unchildlike Behavior: From stealing from the neighbors, to nearly killing his mother, he's proven himself to be as big as a threat as his brothers.
Played by: Jane Kaczmarek
Abusive Parents: Aside from the well known Financial Abuse, she is also implied to be physically abusive, given what Francis commented on what things his brothers should resist in regards to possible methods of extracting who burned her dress, and his resistance to a hazing from a cult on the military school resulted in their adopting Lois's methods. Of course, then again, given his obvious hatred for his mother, it's possible that he either lied about it or led himself to believe it.
She originally intended to subvert it, as she intended to make her household lax of rules specifically because she didn't want to have her children go through the life she herself had to put up with Ida. Unfortunately, Francis as a child proved how faulty that line of thought was when he did several bad things which came to a halt when he attempted to douse his teddy bear with gasoline and set it on fire.
In addition, she herself was a victim of parental abuse via her mother. It is implied to be far, far worse than anything she puts her own kids through, and unlike Lois (who as described bellow acts this way in order to keep her boys safe), doesn't do it to protect Lois, she's just a horrible, spiteful old woman.
Following the incident with the teddy bear mentioned above, Lois had calmly and firmly describe to baby Francis that from that point on she would do everything in her power to keep him and any other child she might have as safe as possible, regardless as to whether or not her kids would hate her for it. Lois knows very well how her kids feel about her parenting, but she legitimately does not care because she's willing to live with them hating her as long as they're safe and alive.
Bitch in Sheep's Clothing: Though viewers almost always see the "Bitch" part she's very good at hiding her true self from people outside of the family. It's implied that she does this to the department of child services.
Control Freak: To the point where a random police officer calls her out on it, along with a Resident Advisor at a school she was visiting with Malcolm, though the RA admitted he was one too.
Determinator: After Reese is sent to Afghanistan she crosses half the earth in order to bring him back home.
Disproportionate Retribution: Played frequently and famously as a major character flaw, such examples would be in Evacuation (She grounds Malcolm for being late home from studying at the library, while insisting on continuing the punishment during a neighborhood-wide evacuation) and Health Scare (where Lois grounds Malcolm and Reese for a week for simply tracking mud on the kitchen floor, even after the promised to clean it up, though it's somewhat justified as she was distracted by a potentially terminal condition Hal had).
Hypocrite: In the episode she gets Malcom a job at her store, in a variety of different way. Malcolm calls her out on it repeatedly given how strict and principled she is at home, but she is utterly remorseless about it, spinning it as him learning harsh lessons about life.
The Cast Show Off: The writers started up a game called "What will Bryan Cranston do?" which led to them writing in plots of him doing roller disco and other bizarre and increasingly dangerous stunts just to see if the actor would ever say no. Not only did he not object, he also kept pulling them off. After this culminated in Bryan being covered in live bees in one episode, the name of the game changed to "What won't Bryan Cranston do?"
One-Hour Work Week: Mostly averted though he is later revealed to have not worked on a friday in fifteen years. Possibly justified by how corrupt the company is and unimportant Hal's contribution is.
Papa Wolf: In the episode dealing with an alternate timeline where Lois had daughters instead of sons, Hal, although overweight, is also extremely protective of his daughters, although his daughters aren't appreciative of his efforts.
Obliquely Obfuscated Occupation: His exact job is somewhat vague though it is known that he works for a large corrupt company and works out of a cubicle. He views it as unimportant and notes he could be replaced easily.
Corrupt the Cutie / Took a Level in Jerkass: Starts off the series as a rather innocent kid (thanks to over protective parents), but then he started hanging out with Malcolm and his family. Downplayed somewhat, however—from his first appearance he's willing to use his disabled status for a Wounded Gazelle Gambit
Handicapped Badass: He started out as quite innocent and helpless but as the series progresses he becomes much more confident. He joined the schools wheelchair basketball team, uses his wheelchair as a weapon against bullies (by running them over) and was revealed as the badass street racer in one episode. Interestingly, a lot of this takes place after his Mom leaves, suggesting it was her over-protectivness that made him under confident.
Manipulative Bitch: Her defining trait, at least to Malcolm and his brothers. Lois, who is herself a Manipulative Bitch, is often able to see right through her. However, she likes her anyway because she is one of the few people who can effectively force (or at least trick) the boys to get along with each other.
Pet the Dog: She had some sociopathic examples of esteem and self-sacrifice which help explain why Lois still cares more than she should about her.
Racist Grandma: To the point where Lois and Francis make a plan with their (African-American) friends to get Ida out of their house so Lois could not have her there when she gives birth. It works too, until her waters break.
This trope seems to be subverted when Ida reveals she's engaged to a man from Hong Kong, but it turns out she just wanted his money.
Parental Favoritism: Towards Susan. And towards his second family over the one he had with Ida.
Grandparental Favoritism: While Victor showed great disdain for Malcolm, considering him to be a "sissy", he took a liking towards Reese, largely because Reese shared his jerkish and violent sociopathic tendencies.
Hilariously Abusive Childhood: Her mother left the family when she was only 3 years old, and her father kicked her out when she was 14 for throwing away his liquor.
Mistaken for Cheating: In one episode, Francis becomes suspicious that she has been meeting with another man while he was at work. It turns out the man was her father, whom she was meeting to chastise for his past Parental Neglect.
Not So Different: Despite their animosity towards each other, she and Lois share many personality similarities. And Francis loves her with the same passion and single-minded devotion Hal has for Lois.
Oblivious to Love: Lois was oblivious to his obvious crush on her during the first few seasons. When he finally confesses his love for her when the store is being robbed, she delivers a "You're Not My Type" speech to him, and they remain friends.
Stalker with a Crush: Displays shades of this towards Lois. Although this was somewhat decreased over the series in favor of increasing his "annoying co-worker" characterization.
Abe and Kitty Kenarban
Played by: Gary Anthony Williams and Merrin Dungey
Beware the Nice Ones: Kitty is initially extremely meek and mild-mannered. After spending a night at dinner with Malcolm's family, she begins to emulate Lois' personality and becomes more vocal and confrontational. She then takes this Up to Eleven after the third season when she snaps and abandons Abe and Stevie to become a porn star.
He later becomes a Jerk with a Heart of Gold in the episode when Francis leaves the academy, acknowledging that he has developed a level of respect for his adversity.
Jerkass Fašade: Later on in "Dewey's Dog," it is revealed that he is actually an extremely depressed and broken man and that tormenting the cadets at military school was the only joy and purpose he had in life.
Old Soldier: Subverted. Despite his numerous amputations and scars, he has never actually served in a war (all of his injuries were non-combat related).
Absolute Cleavage: She wears an extremely low-cut shirt and never misses an opportunity to tell the males around her to stop staring at her cleavage.
Bad Boss: She not only works all of her employees like dogs but also charges them high fees for rent and other basic amenities (such as bedding and hot water) and will deduct money from their paychecks when they fail to keep up with it. She does this on purpose so they have to stay and work for her until they pay her off, which she makes sure they can't do until the logging is finished
Benevolent Boss: Otto is extremely accommodating to his workers. Francis once refers to him as "the best boss he's ever had."
Consulting Mister Puppet: When their estranged son was a child, Otto would discipline him with "Schlupi," a sock puppet. In Gretchen's words, "Schlupi could say all the things that Otto couldn't." Francis eventually gets Otto to reconnect with said son using Schlupi, and later uses it himself to call Lois and tell her that he realizes that she always had his best interests in mind.
Europeans Are Kinky: Francis rewrites a scene from a porno he mistakenly allowed to be filmed at The Grotto to keep it clean for their sake, only to find out they were disappointed that the scene contained no sex.