His relationship with Tenma has a number of possibilities. Was he serious about seeing Tenma as a Father figure and genuinely want to make his life better? Or was he just screwing with him? Or was he screwing with him because he thought it would make his life better?
Broken Base: The ending is considered to be divisive - or, at least, the final shot of the ending.
Complete Monster: This work, dedicated to exploring whether there is such a thing as pure evil, concludes that while anybody, no matter now heinous, can be redeemed, it is Johan Liebert's refusal to seek redemption that makes him the titular monster. A sadistic chessmaster since he learned to walk and talk, Johan murdered his own foster parents and manipulated over 50 adults and children into massacring each other even as a preteen, and, as an adult, Johan is on a personal journey to become, in his own words, as dark as possible. He is also trying to find out if there is anyone as evil as he is out there, or, failing that, forcing the heroic Dr. Tenma, and/or his own pacifistic sister, Nina Fortner, to kill him in cold blood. In this way, he hopes to establish that even the best people can become just like him. Along the way he convinces children to jump from rooftops; gets a recovering alcoholic drunk before throwing him off a building; sets a highly-occupied library aflame; and convinces various serial killers to murder every foster family he has ever lived with, as part of his quest to become an unperson. In the end, Johan tries to manipulate the population of an entire town into slaughtering each other, and, failing at this, prepares to shoot a child in the head just to torture Tenma. Numerous excuses are proposed for Johan's behavior, yet each one is ultimately undermined, revealing that in the end, Johan simply is pure, unadulterated evil.
Draco in Leather Pants: Johan Liebert. Given that he is a fairly attractive young man, this treatment was practically unavoidable. If anything, some fans have a habit of always excusing Johan's actions in a sympathetic light, no matter how flawed the argument is.
Evil Is Sexy: Johan Liebert has a legion of fangirls, mainly because of his physical attractiveness.
Funny Moments: There is an unintentionally hilarious moment when Gustav gets hit by the police cruiser.
Genius Bonus: Aside from the extra understanding gleaned by those with medical degrees, there's a bonus for film or animation students. Lipsky could be a puppeteer just because it's a part of his character, or because it's both creepy and sad...or it could double as a Shout-Out to the Prague school of animation, which, based on when Monster is set, would have still been going strong during Lipsky's childhood. This particular localized trend produced a lot of work based on puppetry and dark fairy tales, both elements which compliment Monster nicely. And of course, Lipsky's first met in Prague.
Jerkass Woobie: Eva. She just wants to fill the hole of having lost Tenma, but does so wrongly by becoming an alcoholic. None of her relationships post-Tenma were successful, maybe except the one with Martin, and then he dies saving her.
Like You Would Really Do It: Will Tenma actually confront the problems of his Thou Shall Not Kill code? Of course not, don't be ridiculous. Possibly subverted by the finale, however. If Johan escaped to continue his rampage, it wouldn't do Tenma's idealism any good.
Johan skips right past it in the first volume and keeps going from there.
Dr. Heinemann crosses it with his total lack of remorse that his political games caused a patient's death, then screwing Tenma's career over and driving him close to the Despair Event Horizon as punishment for saving Johan.
The Baby crosses it (aside from the whole "burn the Turkish district" plot) when he orders Dieter killed for being in the wrong place at the wrong time.
A key theme of the series is whether or not the horizon truly exists. People are redeemed (sometimes at a large cost) for crimes so heinous even death wouldn't be enough in most series. Johan refuses to seek redemption in large part because he considers himself to have crossed the horizon long ago ("Some things can never be amended.") At the end, however, even he is forgiven by his sister, who says "Even if we were the only two people left in the whole world, I would forgive you."
Narm: When Lunge is being strangled he's sticking his swollen tongue out. It's a realistic depiction of strangulation (a combination of the tongue losing circulation and swelling and a last ditch attempt by the body to open the mouth and get more air) and it's also really silly looking.
Nightmare Retardant: Franz Bonaparta's books are supposed to be ominous, but honestly, they try way too hard. And the silly artwork doesn't help.
No Yay: Jan Suk is shown to have romantic feelings for "Anna Liebert", which becomes disturbing in the light of reveal that "Anna" was Johan in disguise.
One-Scene Wonder: Gustav Milch, Tenma's cellmate and prison escapee extraordinaire.
Martin is only in three episodes, but gets enough attention that you'd think he was one of the main characters.
Serial Numbers Filed Off: A doctor chases after a psychopath who is described as "pure evil." Hmm... we're either talking about this anime/manga series or the classic horror film Halloween, except Dr. Loomis is a Japanese neurosurgeon and Michael Myers is a handsome, German young man who plays as The Chessmaster, uses guns, and actually speaks.
Heartwarming Moments: For all the trouble in their relationship, Aileen and Selby do have some pretty cute moments together.
Hollywood Homely : Zig-Zagged. While the makeup, prosthetic teeth, weight gain, and dumpy wardrobe make Charlize Theron look much more "average" than she usually does, it's still hard to disguise the fact that it's Charlize Theron. In an interview on the DVD extras, Theron herself even points out that the real life Aileen wasn't even really ugly, but definitely lived a really rough and harsh life that wouldn't have allowed her to keep a polished appearance and probably even prematurely aged her a bit (the fact that she started smoking cigarettes when she was just 11 years old certainly didn't help).
Hollywood Pudgy: While Theron gained 35 pounds to play the role, she's not that much bigger than average. Wuornos herself wasn't that big◊ either, just out of shape (and her impoverished circumstances definitely couldn't have given her access to things like good nutrition or a personal trainer).
Jerkass Woobie: Aileen. She's an unrepentant criminal and Serial Killer, sure, but growing up in horrible poverty, being abused (physically, verbally and sexually) by several members of her family, being forced to turn to prostitution to survive, getting repeatedly raped and assaulted, and having an undiagnosed/untreated mental illness... is it any wonder that she turned out the way she did?
The easiest way to distinguish Yetis and Wendigos is their preferred flavour of ice-cream: Yetis like Rocky Road, Wendigos go for strawberry.
The ongoing prank war between Monster and Hardy, in which Monster plants one of Liz's dolls under Hardy's car, prompting all four tires to explode and the engine to spontaneously break down... and this in response to another prank in which Hardy sprayed Monster's underwear with Chupacabra pheromones!
The long list of pros and cons of having a succubus for a girlfriend, both of which conclude with "all the sex."
Liz and Monster reflecting on the good times they've had together, including a moment in which she slipped addictive drugs into a batch of cookies at a bake sale - resulting in a feeding frenzy of kids, one of whom actually broke another child's arm with a scream of "that's mine, fatass!"
Judy's growing hatred of Chipper, the impossibly-exuberant waitress at the diner.
When an Inuit walrus dog attacks the diner, Monster is enjoying his meal too much to save the day, and spends the next few seconds loudly talking about how good the sausages and eggs are until Judy shames him into investigating... and then it turns out that the beastie is about to kill Chipper, whereupon Judy assures Monster that he can take his time.
After Greta has her house burned down by an exploding hydra, she needs to call her family to let them know, only to realize she doesn't have her cell phone with her. Monster reluctantly hands over one of Liz's dolls as a replacement, and Greta actually thanks him before realizing what she's just been handed.