Goran, the Russian Contractor in the second season of Darker than Black. He's a Fragile Speedster with none of the Required Secondary Powers. His reaction times aren't enhanced, he's not superhumanly tough, heck, he even gets sore muscles. He is defeated by a contractor whose power is to make it rain, because his superspeed made each raindrop hit with the force of a bullet. He also didn't carry a weapon of any sort, meaning his offensive options were... well he had none. Any attempt to punch or grab his opponent would liquify his arm.
Higurashi no Naku Koro ni: Right, Keiichi, go into that creepy basement with a self-confessed psychotic murderer. Nothing bad will happen. After you survive that, feel free to go out in the dead of night to chat with her. note To be fair, the original game had a decent reason. Doesn't make it any smarter, though.
Princess Amelia, and to a lesser extent, Naga the Serpent from Slayers: the latter is boastful and arrogant to the point that she ignores the reality of the situation around her (leaving Lina to do away with whatever situation they're in), while the former's view of morality is so black and white that she winds up in dangerous situations; anything that turns gray leaves her dumbfounded. While Naga's intelligence varies, Amelia's is more a case of Flanderization that spread to other adaptations - she certainly wasn't this trope in the light novels that the series originated from, and in the anime, at least, she grows out of this trope overtime.
It also doesn't help for Amelia that she's a bit weaker than her companions; while Gourry the ditzy swordsman can fall under this, he generally doesn't because he knows more than he lets on and is more skillful than any other swordsmen in the series.
Mazinger Z: Several characters of the series (including The Hero or its TsundereBattle Couple) get at least one occasion where they seem determined to off themselves. The civilians thought it was a good idea remaining near from the place where a Humongous Mecha and a Robeast were fighting, or blamed the heroes for the destruction and deaths Hell and his lackeys were responsible of, or pressed the Government to yield EVERY TIME Dr. Hell was blackmailing it are good examples. A good, specific example is Yuri, Bratty Half-Pint Sayaka's cousin: Let's go over the facts, Yuri. You are a disabled, little Ill Girl can't run or move quickly because you need a wheelchair. You know there is a giant robot in the city, stomping on buildings and people. Kouji has gone out to stop it after telling you very clearly you must stay in home because you are safer. Still do you insist on leaving the home and go to where the giant robots are fighting because you have a crush on Kouji and you want to see him? Okay, you can leave. After all, what can possibly go wrong?
Many, if not all, of the characters in Ranma ˝ get at least one occasion where they act like this. However, this trope gets played to its actual conclusion in one late-manga story, which really makes it into Mood Whiplash. One character's father receives a scroll detailing a martial arts style which makes use of a lot of brute-force tricks, and a bearhug attack explicitly stated to be capable of snapping a man in half. Kumon Senior intends to use these moves to revitalize his dojo, which is dilapidated to the point it's being held aloft only by a single, rotting pillar, but he decides to master this spine-shattering bearhug by practicing on the pillar. Naturally, when he succeeds in learning it, the whole house collapses on top of him, killing him.
The premise of Kage Kara Mamoru!, in which a family has been secretly protected for ninjas for so long that they've lost the ability to survive normal life. The latest descendant, the female protagonist, therefore has a supernatural ability to walk blindly into trouble, and generally gets rescued before she even realizes what's happening.
Bludgeoning Angel Dokuro-chan: Sakura is this way around Sabato, always offering her a hand even when she had tried to kill him just seconds prior or allowing her to seduce him in her attempts to kill him. To be fair, if she kills him, Dokuro can't.
Jun in Devilman Lady gets episode 1 going by encountering a strange woman (Asuka) stalking her. When Asuka comes to her door in the middle of the night, Jun, despite being afraid, unlocks her own door, willingly gets in a car with Asuka, lets Asuka drive her to a darkened area of the docks, and obediently walks into a deserted warehouse whereupon Asuka locks her in with a werewolf.
Also in Devilman Lady, Jun's girlfriend Kazumi dies when she leaves her hiding place for no good reason whatsoever.
The main character of Kyogoku Natsuhiko Kosetsu Hyaku Monogatari, Yamaoka Momosuke. He has a habit of blindly trusting and attaching himself to even Obviously Evil people, trying to sacrifice himself for others and jumping in to save people from sword-wielding maniacs without any other means to defend himself than yelling "Please calm down!" He'd probably have died at least once every episode if it wasn't for Mataichi's team always saving his ass.
In Inuyasha Kikyou gloatingly tells Naraku EXACTLY why he can't kill her (Onigumo's heart is inside him). As a result he is able to rid himself of it and later use Onigumo's Heart to go ahead and kill her.
In the manga version of Fullmetal Alchemist several members of the Amestris military give Zolf J. Kimblee a Philosopher's Stone so he can test it to see how much more powerful he gets. Kimblee uses it to create massive destruction, upon his return they ask for it back, and Kimblee does what everyone who has spent 5 minutes with the man expects. He swallows the stone then kills the morons who gave arguably the most psychotic person in the series (only Envy is as close) a stone that upgrades his power. Maybe next time they should do some research on the guy they use for their experiment.
Kimblee later suggests that he faked being sane in order to pass the State Alchemist exam. Perhaps everyone except the Homunculi and those in on their plan was fooled.
Dietlinde Eckhart, the main villain of The Movie. She invades Amestris on the mistaken belief that it's Shamballa, which it shares no similarities with, and doesn't even make sense. Shamballa is supposed to be located near Tibet, and Amestris is in another dimension. She then tries to take over the place when the Thule Society has only about 1,000 members while Amestris is a heavy militarized nation with a much larger army. Her army is crushed in about 15 minutes.
Envy itself qualifies. Envy went on a huge rant about how it was the one who killed Roy Mustang's best friend, and almost hurt itself from laughing about it. Envy went out of its way to tell how it was also the one who started the Ishval War and how amusing it was to see such a huge battle over the death of one little girl that it killed. Envy finds itself being tortured with fire about two seconds later.
Loly and Menoly from Bleach are two Arrancar Clingy Jealous Girls who aren't happy to see their boss, Sosuke Aizen, bring a young woman from Earth, Orihime Inoue, as a part of his Gambit Roulette. What do they do? Go torture the girl out of jealous, only to be mauled by their superior. Then, after Orihime shows All-Loving Hero traits and revives/heals them out of pity, what do they do? After a while, they try to kill Orihime again and then use her as a hostage in front of Ichigo and Ulquiorra.
Loly goes so far to claim that she's going to kill Yammy and Ulquiorra, two of the Espadas while she has no special combat ability of her own even if she most likely didn't know about Yammy being Espada #0.
It doesn't help much that the only thing stopping her from being mauled AGAIN is the fact that Ulquiorra, of all people, was forcing Ichigo to continue the fight, saving them... for another ten seconds. They survive though.
Driscoll Berci qualified when he mouthed off about killing Sasakibe to Yamamoto, and used Sasakibe's Bankai against the Captain Commander. He was so stupidly arrogant that he did die by Yamamoto's hands.
A random shinigami from the 13th Division might be the worst yet. Upon sensing a captain fighting something in his jurisdiction, he promptly runs over and starts yelling to find out what's going on, completely ignoring that despite having hundreds (or even thousands) of members, the captain and lieutenant combined equal over 90% of a division's fighting power.
Inverted in Baccano! when Randy and Pezzo's stupidity leads to them becoming immortal.
Isaac and Miria, also Too Dumb To Die, as they'd probably fly under the radar of anyone who could kill them.
Not that they'd be able to anyway; it takes them until they're walking around the modern-day world to realize they haven't aged in about 70 years, and are thus also immortals.
Koukaji in the anime version of the first Saiyuki series. He had previously been beaten with an inch of his life by Son Goku with his power limiter removed, and in the finale, he decides to try and fight him on his own again, and nearly gets killed, again. This wasn't in the manga.
Death Note. The fiancée of the recently murdered F.B.I. agent figures out crucial information on the Kira case and then decides to trust Light with it after he's been acting creepy, following her around, and asking "Have You Told Anyone Else??" Incidentally, she decides to trust Light because he reminds her of L, lampshading that the two are Not So Different.
Someone who uses the name of Kira to pad his own pockets, knowing that Kira is a vengeful god of justice without much sense of mercy. Demegawa? Can you say "SAKUJO"/"DELETE?"note SAKUJO means something like 'eliminate' or 'erase'. It's the catchphrase of Mikami, the 4th Kira. All caps are a must.
Tytania: Duke Idris Tytania betrays another member of the clan he was sent to rescue, and stands by to watch while the enemy destroys his ship, presumably killing everyone on board, including Idris's subordinate, Berthier, who thought he was in on Idris's plans. Berthier actually manages to get to an escape pod and survives, though he is permanently crippled. Then, although he is presumed dead and could easily just take off, he goes back to continue serving the guy that just double-crossed and tried to kill him. Yeah. That works out real well for him, as you'd expect.
Rave Master: Main character Haru Glory's mother Sakura. When someone is telling your husband about how they're going to make him suffer by being alone, you don't run up to them and let them impale you.
Uh, well, Saiou was holding Edo hostage over a pit of lava and threatening to kill him if Judai didn't give it to him, so that may have helped sway Judai's decision a little more... (Also, Saiou made a bit of a dumb move with that himself. The deathtrap was a scale, and to save Edo, Judai had to throw the key on the other side of the balance. It sounded like a good idea, but when Saiou actually went to get it, Neos was able to block his path, which gave Kenzan time to pull Edo out of the way, and that forced Saiou to duel Judia. So, maybe Judai was dumb, but Saiou wasn't all-too smart either.)
Another good example in the franchise was Yliaster member Kodo Kinomiya from Yu-Gi-Oh! 5Ds. Assigned by Godwin to test whether or not Aki was a Signer or not during the Fortune Cup, he knew that Aki had powerful Psychic Powers, was able to literally warp reality during a duel and had very little control over her powers when enraged. Yet, he deliberately tried to make her angry during the duel by insulting her repeatedly. In fact, the original version, as opposed to the dub, doesn't even make clear whether or not he survives Aki's final attack. (Well, maybe you could blame it more on his greed than his stupidity. He had initially demanded five times his usual salary for doing it; eventually, he realized that it wasn't worth losing his life over, and tried to end the duel quickly, but by then, it was too late.)
Divine needs a mention here, after being tricked into revealing he killed Misty's brother not Aki, he then insults Misty's brother, knowing full well Misty is a dark signer and that dark signers have supernatural powers far stronger than his own. And her Earthbound God Ccarayhua, a lizard nearly the size of a skyscraper, is standing right next to her.)
Thinking himself to be the baddest ass of them all, he obnoxiously hits on Revy in an attempt to get her to duel him, then beats the crap out of Rock in order to antagonise her enough to draw on him, until he gets dragged off by Yoshida. This, despite the fact that Rock and Revy are working for Hotel Moscow, whom his bosses are trying to conduct important negotiations with.
He decides to take over the group by kidnapping the heiress to the leadership of the clan with the help of a street gang, and holding her hostage in order to draw out Ginji, her katana-wielding,Badassprotector, to kill him before selling the girl into sexual slavery Predictably, Ginji and Revy tear the Mooks apart, whilst Chaka exits, dragging Yukio with him (and loses her after Rock blindsides him with some cleaning fluid, a bowling pin, and a "Fuck You!".
Later, he comes across Revy again, and again tries to get her to draw, because clearly he can take the woman who just tore through his entire crew like they were nothing. He starts counting down from ten... and she doesn't wait, and instead drop-kicks him in the face and delivers a "The Reason You Suck" Speech, before luring him to a nearby pool... where Ginji is waiting for him to deliver an extremely nasty, but very, very Karmic Death.
The Neo Nazis in general were this. They knew that there was another armed group in the area after the same painting that they were. What did they do after retrieving the painting and driving the Lagoon company away? They started to party. Loudly. With plenty of alcohol and not even a single guard posted. While they had a large supply of firearms on hand. Really, even without Revy and Dutch the idiots stood a good chance of accidentally shooting themselves up before the night was over.
The climax of episode 2 relied on this.
Chen and Louvac are both this. Chen decides to hire Louvac to kill the Lagoon Company traders for working with Balalaika, then proceeds to brag about it to everyone in town, completely ignoring that not only is the Lagoon Company successful for being very good at what they do, but that said skill has earned them a lot of friends in high places.
Louvac and his men not only try to take on Revy (a badass of such renown in Roanapur that her presence bumped a bunch of mercenaries' price for a job from $1,000 to $30,000), but they try to shoot up the Lagoon Company's boat from both side... without staggering their positions, causing two of the boats to take each other out.
Pokémon: Ash Ketchum, during the Pokélantis debacle. He starts off by touching things on suspicious-looking pedestals and sets off a rolling boulder that would've killed the whole cast if Brandon didn't show up. Brandon chews him out for being an idiot. What's Ash do next to prove him wrong? Runs off on his own, touches more things that look very much like they shouldn't be touched, and subsequently gets possessed by a dead king. Brilliant, son.
Ash very frequently acts Too Dumb to Live. If it doesn't relate to Pokémon training, he hasn't a clue how to do anything.
Cameron (Kotetsu), who appears in the second season of Best Wishes!, somehow manages to be dumber than Ash. At least Ash is smart enough not to bring five Pokémon to a full six-on-six battle.
The Red Shirts from the battle against Teppelin in Tengen Toppa Gurren Lagann. Our leader has just obliterated himself against the mysterious shield surrounding our enemy's city? Quickly! More of us must ram into it so that his death will not be in vain!
still trusts the cousin who sold him to pay off gambling debts
after gaining a measure of freedom he goes back to his old house to get a photo album, intending to come right back!
after one of his so called "friends" tries to rape him, follows him into an empty storage room after said friend tells him he's sorry
gets a job at a club which acts as a brothel.
Every single government in Dragonaut: The Resonance. One side commits several outright acts of war, which the other side ignores. The same government then kidnaps one of the dragons, which causes the hive mind of the dragon's homeworld to launch an attack which destroys a space station, and a battle which wrecks most of Mars. Who does ultimate blame get placed on? The rescue party. And in a separate incident, a clearly insane dragonaut attacks another dragonaut over a perceived slight at the spaceport. While a shuttle is launching. When he misses a shot, trashing part of the launch equipment (nearly getting all the other dragonauts killed, as they are in the shuttle), he blames his target for dodging. He doesn't even get reprimanded, let alone receive the court-martial that kind of action deserves.
The torturer in Berserk. Thinking that he has the upper hand because he locked the most dangerous enemies of his kingdom (aka the main characters) in a dungeon room, he proceeds to hang around to taunt them. When Guts slowly stands and asks in an unnervingly quiet and soft voice if he was responsible for Griffith's mutilation, the torturer pays no heed and proceeds to describe exactly how he tortured him over the past year, finishing by showing them his crowning jewel: Griffith's severed tongue, worn as a necklace. His death is brutal, quick and horrifically painful. Worse, he brags how nothing they do will succeed, because the door is three times thicker than any normal door. Too bad he never took Guts' weapon of choice into account...
Frieza has been sliced in half, near dead, and was given a sliver of Super Saiyan Goku's power to survive on as an act of mercy. And what does he do with it? He tries to use it to kill the Super Saiyan from behind, despite the fact that it most likely wouldn't have made a dent. Needless to say, it doesn't end well for the tyrant. He got better, only to get Killed Off for Real by Future Trunks.
Vegeta, to some extent. He has the bad habit of throwing furious raging blasts at his enemies, frequently with enough power to blow up the planet and thus kill himself, from oxygen deprivation if nothing else. Of course, Vegeta would rather die than lose, but he never even considers this detail, even when others scream it at him.
Also, he let Cell absorb Android 18. That was arrogant to the point of sheer stupidity.
The above is rather frequent with Vegeta due to his arrogance. When Vegeta is clearly winning, rather than simply finish his opponent off he'll taunt and play with them, giving them the chance to transform, power up, etc. and then hand him is ass. To be fair, both the heroes of DBZ and the villains will do this as well, but Vegeta does it the most often by far.
Dr. Gero created Androids 17 and 18, who were already rebellious teenagers when they were converted into being far stronger than he whom he had no reliable way of controlling. Then he converted himself into an android, only to base his design on the weaker models. Not content with that level of suicidal behavior, he continues to berate and threaten them despite the fact that he can't control them. His death came quickly.
Videl is a variation of this. She has enough sense not to pick fights she should know she can't win, but she's been known to be insanely reckless in other ways, such as knocking out all the thugs that hijacked a bus, including the one driving it, and then standing around celebrating instead of taking the wheel. By the time a passenger points out, "Hey, Videl! Who's driving the bus?!" they're about to go over a cliff. Since they're unable to stop in time, they do go over the cliff, surviving only because Gohan caught the bus.
During the Buu Saga, Chi-Chi walked up to Buu and slapped him while yelling at him for killing her oldest son. She gets turned into an egg and squished.
There's Bardock, who knows far in advance that Frieza is going to destroy his home planet. What does he do? Thanks to a double dose of both Honor Before Reason and Revenge Before Reason he decides to take on Frieza in a bid to stop him from destroying Planet Vegeta, despite knowing perfectly well that he was FAR too weak to stand a chance in hell against Frieza instead of getting in the nearest pod and getting the hell out of dodge and maybe coming back when he did stand a chance.
Ookami Kakushi gives us Hiroshi. He's prone to things like staying in a car with someone making creepy advances on him, walking around town at night after witnessing a brutal murder, specifically walking around the areas another classmate warned him to stay away from, seeing nothing suspicious in being called up at night or being asked to go into an abandoned barn...
Isuzu, for the most part, manages to make the right decisions to stay alive until episode eleven, wherein she sees the villain (whom we should add is highly unstable by this point in the story) walking through the forest. Instead of reporting it to the authorities, she decides it would be a better idea to follow them into the forest alone. While wearing bells tied to her wrist. This Ax-Crazy has a gun.
In Char's Counterattack, the Earth Federation makes Char promise not to drop any giant space rocks on them...and pays him off with a suitcase full of money and a giant space rock. Guess what happens next. No, seriously, guess. Also, this film also marks the death of the titular character. Guess who is responsible for his death. Taking lessons from Vegeta, Char?
Sailor Moon: Because Usagi/Serena is such a klutz (as well as a crybaby), the other Sailor Senshi/Soldiers/Scouts, and the two cats started pegging her as this (or at least that's what DIC's English version would like us to think...). However, this applies more to the anime than to the manga (especially the crybaby part).
Run from A Channel. In the first episode, she almost falls out of a third story window while waving to Tooru on ground level outside, and is only saved when Nagi and Yuuko grab her feet and pull her back in.
In Code Geass, there are a few characters that fit. Tamaki has a tendency of rushing into things, despite having no special combat talents, and survives most battles only by luckily ejecting from his knightmare as it blows up. Nina Einstein is this as well, during the incident at the lake hotel. Girl, if you're faced with an angry rebel of the island you forcibly conquered, don't call him the derogatory nickname that your homeland gave them!
Suzaku is a subversion of this trope: he wants to change the government of Britannia from the inside by joining the military, even though it discriminates against his very people, including himself, and such a position involves putting down his own people to prove his loyalty. It's through sheer luck that he manages to make any progress. The subversion? He's doing it all to fulfill a secret death wish.
Nunnally herself also counts. She is more in the right mind, and position, than Suzaku, as governess of Japan, plus the ability to detect lies. Not using the latter on Schneizel, who lies to her about Lelouch and Pendragon being evacuated, and later uses her as a pawn in his latest plan with no aversion to abandoning her: big mistake.
Joseph Greer fatally shoots Alyssa with Miyu nearby, but does not run away immediately afterward, instead announcing his intentions for doing so. Within moments, an enraged Miyu kills him.
During her confrontation with Shizuru, Haruka not only unnecessarily insults Natsuki, but continues to insult Shizuru even as her Element is drawn rather than stop provoking her or run away as Yukino suggests, thus forcing Yukino to try to defend her, leading to the destruction of Yukino's CHILD Diana, and Haruka's own death.
When Nao first encounters Shizuru while attacking Natsuki, she is easily defeated. In response, she kidnaps Natsuki again, this time for the express intention of luring Shizuru out. To make matters worse, by this time, Shizuru has gone insane from Natsuki's rejection, and not only destroys her CHILD Julia, but tries to finish off Nao before Natsuki intervenes.
Kanaria from Rozen Maiden has some shades of this during the series, but it becomes blatant obvious during the final battle of the second season: not only she is the cause of turning Suiseiseki's Heroic Sacrifice in a Senseless Sacrifice by going back to the battle field, she also is killed by Barasuishou after the strings of her violin snaps and she forgets that, since she has Suiseiseki's Roza Mystica, she could use her Green Thumb powers.
Akko-chan, from Himitsu no Akko-chan, in the aptly named '_____' episode asks her magic mirror to make her deaf and mute, thus, more empathic to the new deaf kid in her class. After realizing that she just wished herself mute, and her magic mirror could only obey to spoken commands, she spends the whole episode as a non-verbal deaf girl, moving from curiosity to deep-rooted depression. Keeping her rationality until the realization of her newfound handicaps kicks in, she then starts acting in a completely unreasonable way, ranging from acting as she were completely uncapable of any kind of communication to running blindly in a dangerous, isolated place, knowing that, being unable to cry for help, she'd risk falling in a ravine and being left there to starve. Exactly what happens to her. On the top of it, the deaf boy "inspiring" her wish sees into her self-destructive ideas and manages to save her from certain death.
The last Saitama team in Initial D's fourth season calls a bunch of gang-banger types to beat up Project D and neglects the fact that the gang-bangers are from the same region as Project D and thus likely to be fans and that the owner of the car they forced into a wreck during the practice runs (using a cheap trick of spilled oil) was the former boss of those same gang-bangers. The current boss was NOT amused at being made to look bad.
The Fake Straw Hats in One Piece'. Notably, they picked fights with members of the actual Straw Hats despite being very weak (to be fair, Usopp's wanted poster doesn't show his facenote but instead shows his alter ego, Sogeking, both he and Nami had changed looks during the Time Skip, and Luffy was wearing a ridiculous Paper-Thin Disguise, so they hadn't recognized them) and tried to hunt them down after being casually defeated and mauled by them.
Their plan to take on the New World involved using Luffy's reputation to recruit an army of powerful pirates, then sending them out to take out any danger that the aforementioned reputation didn't scare away first. This might seem like kind of a clever plan at a casual glance, but the New World is loaded with pirates who still consider Luffy a rookie, and could honestly care less about his accomplishments up to that point; not to mention there are numerous obstacles and dangers that are far too much for any pirate that was available on Saobody at the time, or simply require knowledge or skill rather than muscle to navigate. Not only that, but they also attracted the attention of pirates who were only joining so they could kill Luffy unawares in order to boost their own reputation. Sentomaru, sent by the Marines to arrest them because their informants had mistaken them for the real deal, actually called them morons for impersonating the Straw Hats after mauling the fake Luffy.
What added to their misfortune is that around the same time they started recruiting, the real ones were about to reunite and journey into the New World. Really, a combination of bad luck and stupidity ensured that the Fake Straw Hats were never going to make it out of Saobody.
Oh brilliant idea Hody! Mass produce the Energy Steroids and pop them by the dozen like candy! What could possibly go wrong?
Something similar happens not long after, though in this case, it's more like "Too Dumb for Everyone Around Her to Live". Before Grimoire Heart came to attack, Fairy Tail was in the middle of an exam that Cana was taking very seriously to the point that she threatened to leave the guild if she failed. So what's the best thing to do when a bunch of uber-powerful opponents have come to fight, inadvertently interrupting the test in the process? According to Cana at the time, it's continuing to take the test as if there weren't any enemies to begin with, instead of helping her friends fight when some of them are falling left and right. To her credit, she didn't realize that some of her friends have already fallen, but what does she do next? After Lucy gives her a lead on how to pass the exam, she knocks out Lucy and abandons her to do just that. And this is while knowing that there are enemies powerful enough to kill them wandering around. And Lucy would have been killed if she hadn't woken up at the last possible second. Again, to Cana's slight credit, she did try hiding Lucy out of sight from potential enemies. But that didn't stop Lucy from being found anyway. Similar to the above example, however, Cana eventually recognizes her own idiocyand rushes to her friends' rescue.
The Tartaros arc features the titular guild, whose members are legitimate demons, trying to activate a powerful magic. To unlock this magic's seal they need to kill certain members (current and former) of the Magic Council, but don't know which ones, so they just opt to kill them all until they succeed. There is one, however, who is subverted to their purposes and helps them find the last former member with a seal. To save the trouble of tracking him down, the traitor takes the last part of the seal into himself, with the intent to give it to someone else so they can be killed and break the seal. He tells Tartaros' members this after doing it to himself but before doing it to anyone else. He's immediately Rewarded as a Traitor Deserves.
The female assistant in the first episode of Elfen Lied. The moment she saw the devastation that was being caused you would have expected her to realize that a noncombatant like herself should do the smart thing and get to the exit ASAP.
In Axis Powers Hetalia, Italy is such a Distressed Dude that it's a wonder he survived until Germany formed an alliance with him. One notable example is when Germany tries to teach him how to throw a grenade. Italy throws the pin, leaving the grenade clenched in his mouth. He then just sits there blankly, while Germany screams at him to throw the grenade before they both get blown up. Romano later does the same thing, suggesting that this trope runs in the family.
Humanity to a certain extent in The Animatrix segment, "The Second Renaissance Part 2". They basically cause their own defeat by blocking the sun, without any objections and without thinking or using common sense, to try to cut off the machine's power supply, but it also kills Humanity's vegetation and it cuts off Humanity's Vitamin D (ouch), and the humans were not able to adapt to this and are ultimately defeated by the machines.
Adolf Junkers in Monster. First he runs straight into traffic, then he sees a security guard fall down dead, leaves his room, and runs into an unlit area at night. When he knows someone really nasty is trying to kill him. Is anyone surprised when Junkers is found and shot to death?
Richard Braun, who's investigating a string of serial murders, more or less deduces that Johan's behind them all. Yet he doesn't think he should tell anyone when Johan shows up at his apartment and invites him out. Shortly after this, he follows Johan up to an abandoned rooftop (in the middle of the night) while shouting, "I know what you're up to, kid!" To no one's surprise but his own, it ends badly.
In the Cross Fire omakes for Hellsing, a cult honestly expect Heinkel and Yumie, who they (correctly) believe to be Vatican assassins to leave simply because the cultists insist the church is a holy site. The same assassins that are there because members of said cult launched a chemical attack on the Vatican and tried to assassinate the pope then publicly took credit for the attack. Naturally Heinkel and Yumie kill all of them.