Demetrius: If it only worked that way, I would be very happy.
Sam: Can I be the devil on your shoulder? Just do it, fight the monsters!
Demetrius: Maybe later.
A great sign of wisdom is the ability to measure your own strength as compared to your opponent's. After all, in order to know how strong you are, you must first know how weak you are.
This is the trope for when a fighter bows out of a battle he can't win, or at least knows that his enemy is much stronger than they look. Perhaps it's because he or she is Weak, but Skilled, and has a keen enough eye to see why the other dude is so powerful. Or maybe his Stat-O-Vision lets him recognize that his enemy's Power Level is Over 9000! Whatever the case, he knows he can't win, or at least knows that Underestimating Badassery is a bad idea for those in love with breathing.
This could be seen as a Sub-Trope of Know When to Fold 'Em, showing us why a character would give up a fight without trying. Enemy Scan and Readings Are Off the Scale could be how they learn the strength of their opponent, and Screw This, I'm Outta Here! can be the final result.
- Dragon Ball was notorious for this, especially during the later part of the series. Often if you weren't a Saiyan, all you could do was sense that your enemy was way too powerful for you to even think of fighting against.
- When Tenshinhan was fighting Tao-Pai-Pai, the latter could find no flaws in the former's defense, leaving him unable to attack at all. It seemed to work both ways, but Tenshinhan was actively choosing not to attack to let Tao see for himself just how outmatched he was.
- In the early portions of the Buu Arc, Piccolo forfeited when he realized he was fighting the Supreme Kai / Kaioushin. He knew right away he stood no chance of winning, and dropped the fight at the first opportunity.
- Vegeta tends to subvert this, as he has a bad habit of misjudging his own power compared to his opponents, which stems directly from his biggest flaw. It got him killed against Frieza (after he convinced the former to reveal his true form), and caused the rise of Perfect Cell as well.
- While gung-ho at first, everyone who isn't a Saiyan or half-Saiyan decides not to participate in the "Cell Games", knowing they have absolutely no chance against Perfect Cell.
- In Pokémon Adventures, Blue forfeits to a wild Mew because he knows his Charmander isn't strong enough to win. Red, at the time an Idiot Hero, plowed ahead and got beaten easily.
- Meanwhile the anime has Paul vs Cynthia. It's played with at first, in that Paul challenges her to a full battle, and she starts with her strongest Pokémon, Garchomp. We watch as she steamrolls every Pokémon he throws at it. However after he gets it to use Giga Impact, he reveals that he never wanted to fight all her Pokémon; he only intended to see if he could beat Garchomp, and brings out his strongest Pokémon to take advantage of Garchomp's weakness. He still gets flattened by Garchomp however, and gives up when he realizes he can't beat all her strongest Pokémon even with all of his. So he knew he couldn't beat her whole party, but still hoped he could take at least one of them with the right plan until the situation proved otherwise.
- Played with In Mahou Sensei Negima! This dude is smart enough to realize that his opponent is not someone to be trifled with and wisely decided to stay on guard. The Result? Well what did you expect? It's Evangeline.
- Subverted in Soul Eater. Early on, Maka gains the ability to detect soul wavelengths while fighting Prof. Franken Stein. She sees how powerful he is but Soul convinces her to stand her ground anyway. This causes Stein to give them both a passing grade.
- In Code Geass, Suzaku, with his Geass to live no matter what, senses that an opponent who seems to be easy, has his Geass screaming in his head to run. Turns out the opponent had a Geass of his own, that let him see a few seconds into the future, and was able to deflect any attack against him.
- Happens a number of times in the Vagabond manga, usually when characters confronting either Miyamoto Musashi or Sasaki Kojiro realize they're in over their heads. Justified, since a skilled swordsman who wants to make a name as a swordsman should have an idea when he's biting off more than he can chew. Surprisingly enough, despite his reputation as an Invincible Hero and being the main character, Musashi has also had this happen to him a few times.
- The series follows the same trend as Dragon Ball by having characters gauge each other based on sensing the others spiritual pressure. If someone has an Oh, Crap! reaction, it's usually a good indication that they're out of their league.
- When Head Captain Yamamoto faces off with Kyoraku and Ukitake, the sheer magnitude of his spiritual power causes Nanao to suffer a full-blown panic attack.
- Defied during the final battle between Ichigo and Ulquiorra. The fourth Espada takes his power level through the roof to demoralize Ichigo, but the hero already knew going in that Ulquiorra was way stronger than him and decided it didn't matter because there was too much riding on the battle for him to back down.
- Inverted in the case of Kisuke and Isshin facing Sosuke Aizen, and being utterly unable to sense his power. The fact that they can't sense it even though the guy's obviously strong is an indication that he is WAY out of their league, no matter how much energy they manage to release. Only someone who could sense it would have the potential to match him. This later gets turned around on Aizen when he can't sense Ichigo's power despite Ichigo clearly displaying his own abilities and suffers a Villainous Breakdown when he realizes what that means for him.
- Fairy Tail. In the S-Class Exam, Gildarts unleashes his full power in order to teach Natsu to do this. Natsu briefly tries to charge Gildarts but is quickly forced to admit defeat.
- Asura Rhino in One-Punch Man instinctively leaps back when Saitama glares at him since all of his senses are warning him not to fight Saitama. Unfortunately for Rhino, he decides to ignore what his instincts are telling him and attacks again.
- In the Marvel Universe, the mutant Darwin has the ability to possess whatever power is necessary to survive a given situation. In one instance, Darwin finds himself facing off with The Incredible Hulk after the green giant had just returned from Sakaar and was angrier and stronger than ever before. Darwin's ability does indeed allow him to survive the encounter... by immediately teleporting him several states away before the fight even starts.
- Death Is Forced To Take A Vacation: Discord knows he's this the instant he recognizes Fall Harvest as an Adjunct of Death; even with his status as the Lord of Disharmony, Fall Harvest outranks him, and he knows better than to mess with anyone under the employ of a Lord or Lady of Death.
- FateBlack Reflection: When Ichigo and Shirou finally come face-to-face, Shirou has the misfortune of staring down the business end of the substitute soul reaper's bankai after he arrives to save Rider from Saber. Shirou has no idea who or what he is, but his newly developing spiritual senses tell him that Ichigo could end his existence in a second if he felt like it and there would be nothing the magus could do to stop him. The encounter leaves Shirou thoroughly rattled.
- At the beginning of The Matrix, an unarmed Trinity defeats two units of armed police officers single-handedly. As soon as she sees an Agent, however, she starts to run for her life. Because Agents can possess anyone still stuck in the Matrix and can take apart many Free Minds, trying to fight them is suicide at least until Neo becomes The One.
- In Sherlock Holmes: A Game of Shadows, Holmes displays his signature Awesomeness by Analysis via Sherlock Scan ability when about to fight Moriarty. The Scan reveals that in his currently weakened state there is no way Sherlock could survive a fight with Moriarty, so he has to Take a Third Option.
- In Attack of the Clones, Count Dooku challenges Yoda to a lightsaber duel after wiping the floor with Obi-Wan and Anakin, in that order. He holds his own but decides to flee when he's unable to defeat his old master.
- Assassin Of Gor
- Cernus, in order to torment a condemned prisoner, offers him a chance for freedom. If the prisoner's champion beats his champion at a chess-like game, the prisoner will go free. Cernus chooses a proud young prodigy named Scormus from himself and a homeless mentally disabled "fool" for the prisoner. The fool spends most of the time screwing around, and everyone's convinced he doesn't understand the game and his moves are random. Scormus, however, realizes early in the match that the the fool is better than he looks, and eventually yields the game to him. He's soon proven correct when an enraged Cernus takes over his position and loses as predicted.
- Unknown to Cernus or Scormus, the "fool" is Scormus' father, bred from a slave who has also shown great proficiency in the Game (despite the Game being forbidden to slaves). That's where Scormus gets his great skill from. Also, earlier in the same scene, Scormus refuses to play against the "fool" because it would do dishonor to the Game and insists that he be allowed instead to play against Qualius, another Player who is in attendance. Qualius knows his and Scormus' levels of skill and assures Cernus that he (Qualius) would lose.
- In Warrior Cats, there are several instances when cats realize they cannot win: for instance in the prologue of the first book Redtail orders the ThunderClan patrol to retreat from the battle at Sunningrocks when he realizes that there are just too many RiverClan warriors and that his cats are losing.
- In Justified Rayland is a Cowboy Cop and Fearless Fool who tends to take risks and succeed because he is more skilled and determined than his opponents. However, when he tries to intimidate Limehouse into giving him information, he ends up in an armed standoff with Limehouse's men. Rayland realizes that Limehouse is one of the few criminals in the area who are not only unafraid to kill a U.S. Marshall but are also capable of making the Marshall's body disappear without a trace. Realizing that he cannot bully or bluff Limehousem, he instead appeals to Limehouse's honor so they can end the standoff peacefully. It is one of the few times on the show that Rayland is really scared for his life.
- Burn Notice has a moment of this when Mike and Fiona are protecting a bail jumper while trying to prove him innocent. The bounty hunter that they originally rescued him from is well trained and, in Mike's words, has "six inches and fifty pounds" on him.
Michael: Ohh, damn.
- On Cuchulainn's blooding, his first combat as a warrior, he sought out three brothers who were renowned fighters and defeated them all. One of the brothers had the ability to instantly judge his opponent's abilities at a glance, and upon seeing Cuchulainn, immediately surrendered. But because he was afflicted with berserk rage, Cuchulainn killed him anyway.
- Following former champion Chris Hero's example, Drew Galloway would announce he was putting the EVOLVE title on the line even when the match wasn't supposed to be a title match...only to be denied by the referee, who insisted Galloway couldn't do that because a new ranking system to determine title contenders had been put in place since Galloway beat Hero. When Galloway went against Open The Freedom Gate champion Ricochet, who logically should have been eligible for a title shot, Galloway didn't seem to have an issue with the EVOLVE title not being on the line.
- In Skies of Arcadia, Vyse immediately knows that he and Aika are no match for Galcian and advises her to run instead of standing their ground. If you ignore him or don't run fast enough, Galcian will curb stomp you into a premature Game Over.
- In Undertale, the final boss of a Genocide run will eventually decide that he can't beat you properly, so he pulls out his special attack: refusing to ever end his turn, so you can't act and will be trapped forever.
- In RuneScape, most monsters become non-aggressive when the player character's combat level is more than double theirs and won't attack unless provoked.
- In Vampire: The Masquerade Bloodlines, most civilians immediately run away when they see combat, and even the police retreat if the player character starts using the flashier vampire powers like Super Speed or Blood Magic — although doing so is a quick route to getting Killed to Uphold the Masquerade. In the World of Darkness, choosing your battles is a vital survival skill.
- Invoked in The Order of the Stick when Vaarsuvius simply informs Laurin how many spells s/he has remaining, trusting that she'll be able to work out what this means about their respective power levels and remaining resources from that and what she's already seen V do. She does, and promptly teleports away.
- El Goonish Shive: Nanase claims that her Guardian Form's combat instincts are telling her she can take on Not-Tengu, in an attempt to get her friends to run away while she buys time. Actually, her Form's instincts were basically screaming at her not to attack this guy; as powerful as her Guardian Form is, Not-Tengu is leagues stronger. When Ellen copies the Guardian Form and arrives at the same conclusion, they come up with an alternate method to defeat the monster.
- Dragon Ball Z Abridged follows the same trend of its source material of characters realizing how screwed they are when they sense another characters power, with it's own twists. The most notable example happens when Cell achieves his perfect form and everyone has a Mass "Oh, Crap!" moment upon feeling his overwhelming power, including Bulma, who can't even sense power levels to begin with.
Bulma: Hey, so, I can't sense power levels, but I can feel that. Does that mean anything?
Piccolo: We're fucked.
- In Real Life (and for any situation, not just sizing up an opponent) this is known as the Dunning-Kruger effect. More specifically, that it means skilled people are both more able to recognise skill in others, tend to underestimate their own skill and often make the mistake of assuming others are equally skilled (less skilled people are the opposite).