On one end, we have the Horrible Judge of Character; the character who couldn't tell a bad guy if it hit them in the face. They trust the Obviously Evil characters, dismiss any and all claims of their true personalities, and are typically totally oblivious when it comes to who can be trusted or not.
But on the opposite end, we have the character who is able to tell a bad guy with just one look! They see the evil in their eyes, the cockiness in that smirk, and the deceit in their voices that some of the other characters just can't see. As such, they can sometimes be Cassandra Truth people who try to convince everyone else of the bad person's true intentions only to be dismissed or brushed off. They're told that they're "jealous", "mean" and "overreacting" along with some other things that show how oblivious the person they're trying to convince is.
However, while that is often the case, it doesn't always have to be. Sometimes, another character will listen to them.
And this doesn't just have to be about knowing who's an antagonist when the other characters usually don't. Sometimes, being a good judge of character is about knowing who to trust and having it pay off. When someone switch bodies and don't know it, they can sometimes feel or see that something wasnt right as they tried to find out the answer or figure it out on their own, which could also led the answer to come to you, especially when the good guy would be trapped inside the bad guy's body.
Contrast Horrible Judge of Character. Not to be confused with Detect Evil, where someone uses magic instead of their instincts to determine antagonists. When an animal has this skill, that's Evil-Detecting Dog and sometimes Licked by the Dog. Can overlap with Cassandra Truth. Also compare Evil-Detecting Baby, where a baby is able to tell when a certain character is evil, usually by crying in their presence. May overlap with Living Lie Detector, which provides obvious advantages in assessing someone's trustworthiness.
- Lacus Clyne in Mobile Suit Gundam SEED proves to be this despite her young age, in addition to being an inspirational political figure. Throughout the series, she has entrusted power to several unlikely individuals (most notably, Kira, then a soldier fighting against her country), but has yet to experience a serious betrayal of her trust.
- Hans Georg Schubert from Monster was able to figure out how evil Johan Liebert was on his own because of how "perfect" he was acting. He knew that Johan couldn't have been any ordinary human being what with how intelligent and skilled he was at basically everything. He also drew this conclusion from noticing the parallels between himself as a young man - who wanted to be a beyond-human, chaotic monster - and Johan, who is most certainly those things. And this is before he saw firsthand what Johan was capable of, unlike Tenma, Nina, and Reichwein.
- One Piece: Despite being an Idiot Hero, Luffy is a phenomenal judge of character, which combined with him being a Magnetic Hero means that anyone he chooses to place his trust in almost invariably becomes a lifelong ally (even if they were originally planning on betraying or killing him).
- Speedwagon from Part 1 of JoJo's Bizarre Adventure accurately discerns Dio Brando's wicked nature upon first whiff.
- Demon Slayer: Kimetsu no Yaiba: series' lead Tanjiro Kamado is an expert at telling a persons true nature not long after meeting them; two shining examples are his encounters with Shinobu and Zenitsu: with the former Tanjiro is able to tell Shinobu harbors some deep anger under her constant pleasing smile that impresses the Hashira enough to tell him the reason why, with the latter Tanjiro is able to tell Zenitsu is actually a very strong demon slayer right away, despite Zenitsu repeating numerous times in their first encounter that he is weak, it reaches the comical irony in which Tanjiro is actually surprised to see, in the Red Light District arc, that Zenitsu has to rely on his trance sleep mode to unleash his full strength, while other people, like Inosuke, had to see Zenitsu during that state to see that he was strong after all. He isn't wrong about it either, since the time where Zenitsu fights without the influence of the trance, he's indeed powerful enough to create a technique to defeat his traitorous colleague, and later to gain an inch in the fight against Muzan.
- Greninja, as Froakie, knew that Team Rocket's Mewoth was up to something when they got separated from their Trainers.
- Pikachu got suspicious with Chairman Rose the minute he meets him as he felt something was off about him and was secretly glad that Ash declined his offer to help him achieve his goals.
- In The Walking Dead, when Magna and the group of survivors that she leads first encounter Rick and the Alexandria Safe Zone, they're deeply suspicious of the main characters, especially the fact that they insist on disarming the new survivors. This makes them worried that Rick and company mean to kill them and that Alexandria is a Town with a Dark Secret. This would seem to be confirmed when they poke around at night and find Negan, the Big Bad of the previous arc imprisoned and claiming that Rick is a cruel despot who has had him tortured. The other members of the group are ready to jump on this as proof of their suspicions, but Magna almost immediately sees through the story and realizes that Negan is trying to con them into freeing him. When asked about it, author Robert Kirkman credited Magna with having "a really good bullshit detector."
- Kat from Tales From The Spirit Lands has been able to detect bad intentions in her father Mejuri, who turns out to be an abusive Jerkass, Farai, who even after protecting her from Kheri, made Kat uneasy to be around and she turned out to be a child murderer, molester and rather manipulative, Scar, who we all know as The Lion King (1994)'s main antagonist who murdered his brother and attempted the same with his nephew, and Kheri, who she disliked right from the start, and he turned out to be a murderer and rapist!
- In The Shield's Dragon, former yakuza Kazuma Kiryu can effectively tell who in Melromarc can be trusted and able to see through most of the bullshit perpetuated by the Royal family, the Church and the other three useless Heroes when it comes to the Shield Hero's reputation due to decades of experience in Japan's criminal underworld resulting in superior maturity. It does help that Julius Harken, a former Royal Court mage had warned him about all of them in advance, but even then Kiryu doesn't fully take that information at face value until he sees it for himself.
- The main heroes of Showa & Vampire are almost all said to be one of these, as an easy explanation of why people should trust them vouching for somebody they like who happens to have a dubious background. Always a beautiful girl who will end up falling hopelessly in love with the "good judge of character", one notices.
- In Code Geass: Paladins of Voltron, when Princess Euphemia sees Haggar, she immediately realized that there is something off about her, which was why she chose to escape with Lelouch after seeing how terrified he was of her.
- In Code Prime, when Euphemia first meets Megatron, despite telling her that they have the same goals, she could tell just by looking in his optics that he wasnt telling the whole truth.
- In Disney's 101 Dalmatians, Roger is this towards Cruella. He is the one who invented the song "Cruella de Vil" after all. Just listen to the lyrics! Not to mention that he remembers how much Cruella wanted Pongo's and Perdita's puppies and how aggressive and angry she got when she couldn't have them. As such, he proclaims her to be his "number one suspect" after they're kidnapped, even after Anita argues against his accusations. Turns out he was right about this, even though he doesn't find out in the end.
- The Sultan from Aladdin claims he's one of these. He's right about Aladdin, but on the other hand, he also thinks Jafar is a reliable right-hand man up until the last part of the movie...
- At the beginning of Jurassic Park, John Hammond claims to be able to do this when he tries to sweet-talk Dr. Grant and Dr. Sattler into endorsing his park (invoking the idea that people who can do this are nice). Of course, he also trusted Dennis Nedry with designing the park's systems and having full access to the network, so perhaps his mouth is writing checks his eyes and ears can't cash...
- John Mason in The Rock claims that he can tell that neither Goodspeed nor Hummel are willing to kill innocents. He's right on both counts.
- Joked about in The Eagle Has Landed. When Devlin discovers a way for the Germans to escape the church they're trapped in, Steiner says, "Mr. Devlin, you're an extraordinary man." Devlin responds with, "Col. Steiner, you're an extraordinary judge of character."
- The Dresden Files has Agent Tilly, introduced in Changes, is very good at telling when people are lying to him, so good that Harry suspects he has some latent magical talent helping him along. As a result, he's a very good judge of character. In fact, he develops a quick dislike for Rudolph (who is generally an asshole and turns out to be a pawn of the Red Court) and pegs Harry as trustworthy almost immediately.
- The French Lieutenant's Woman: Sarah is said to be very intelligent, and her intelligence is connected to judging people correctly and knowing their worth. The narrator even compares her ability to tell if someone is good or bad to some kind of computer. For example, she immediately recognizes that Mrs Tranter is a kind woman whom she can trust and she's similarly drawn towards Charles.
- A Song of Ice and Fire: Arya Stark, at all of 9 years old. From the get-go, she dislikes Queen Cersei and Prince Joffrey, even while her sister Sansa is fawning over them. As a prisoner at Harrenhal, she develops a skill for recognizing the cruel guards from the safer ones, and doesn't reveal herself to Roose Bolton despite him being a Northern lord and (allegedly) sworn to her brother. The only character she does trust with her true identity, Gendry, comes through as a rare decent person and loyal friend. The fact she's less blinded by status than most nobles helps and she contrasts painfully with her parents and older brother and sister, whose Horrible Judge of Character is their Fatal Flaw.
- Good Luck Charlie: Charlie hit and bit Teddy's boyfriend, Spencer, because she felt something was going on with him. However, Charlie was proven right when Teddy caught her boyfriend cheating on her and breaks up with him.
- Lab Rats:
- Leo realized that Marcus was evil the minute he met him and tried too convinced everyone about it but no one believed him. However, the Lab rats and Davenport realized that Leo was right about Marcus when he showed them his true colors.
- Perry got suspicious with Sebastian but no one believed her until it was too late when he revealed himself and his plan.
- Rocky in Shake it Up, realized that Deuce's girlfriend at the time Savannah was a gold digger as she realized that she got back together with him was because of money. Instantly, "CeCe" and Ty believed Rocky as they work together to exposed Savannah to Deuce.
- In stark contrast to Tony, Junior has this ability in The Sopranos.
- Odo in Star Trek: Deep Space Nine, as part of his overall skill at deduction and analysis.
- This is a trait of the Septim family in The Elder Scrolls series. In particular, Martin in The Elder Scrolls IV: Oblivion knows immediately that they can trust the Player Character (the Emperor does too, but he had the benefit of a prophetic dream).
- In the backstory of Pillars of Eternity, Iovara The Heretic was known to pick her allies very carefully, which allowed her to evade the at-the-time all-powerful Inquisition for as long as she did. The only time she was wrong about a person was with the previous incarnation of the Player Character, who ultimately betrayed her to the Inquisition, although how wrong she was is left up to the player to decide.
- Arthur Morgan from Red Dead Redemption 2 seems to have a perfect judge of people. Particularly he's confident about John Marston being loyal to the gang, one of the few to notice Dutch's changing behavior and knows from the beginning that Micah shouldn't be trusted.
- In Mass Effect, Urdnot Wrex informs Shepard that he was once offered a job from the games Big Bad Saren. Wrex then mentions that the instant he saw him, he suspected that there was something off about him, so Wrex decided to leave before he accepted the payment. Wrex then tells Shepard that he was right about Saren, as all of the other Mercenaries who took the job were killed a week later.
- Ace Attorney: Zak Gramarye was an asshole in life, but one thing he was good at was judging people's character. He instantly pegged Kristoph Gavin as a monster, while noting Phoenix Wright as a man of honor and someone he could trust his daughter with. He was right on both counts.
- In The Order of the Stick, Haley is the best at analyzing the motives of others. She determined that an early character is evil, while everyone else insisted that they should cooperate. That character became a major recurring villain.
- Black Jack Justice: The episode "The More Things Change" features a client who wants to get married, but her great aunt, the family matriarch, is against it because she harbors suspicions against the fiancee. This leads the client to hire Jack and Trixie to prove her would-be husband is a good and virtuous man. Unfortunately, what they do instead is find out he's a crime banker, a man who gives criminals loans to finance their crimes. When the client refuses to believe any of this, Jack lays it out to her that her great aunt's good instincts for people seeing something wrong with the fiancee, even if she didn't know what, are saving her from herself.
- Sokka from Avatar: The Last Airbender is this. He's usually the only person in the Gaang to tell if someone has bad intentions or not, and he's often brushed off as a result. An example would be with Jet.
- Batman: The Animated Series:"
Batman: Joker had you pegged for hired help the minute you walked into Arkham.
- When Harley explains her motivations to Batman, he has a good laugh at her expense. Then he delineates exactly what kind of person the Joker is, how he really sees Harley, and without telling her, calculates correctly that her obsession for the Joker may be used to hand her a self-defeat.
- The Joker towards Harley Quinn as well, just as Batman tells Harley:
- Teenage Mutant Ninja Turtles (1987):
- In "The Old Switcheroo", after an accident caused Splinter and Shredder to switch bodies, the Turtles and Krang felt something was off with respective friends because of their personalities because Shredder in Splinter's body made it easy for them to notice, which became clear during a training exercise and the way he was treating April, while Splinter in Shredder's body was being nice. However, Krang ends up shrugging off his suspicious when he brain scanned Splinter in Shredder's body, but was unaware that he had been played because he controlled his brain waves in order to match his enemy's, while the Turtles realized that they were right to trust their instinct as their master came to them and explained everything.