Kushan underofficer Kanishka:How are we supposed to be an imperial bodyguard if the damned Empress herself... Kushan commander Kungas:You could always go back to work for Venandakatra. He never took any personal risks.
If you're important, then it's best to stay safe; all sorts of people might bear a grudge toward you for your decisions, because of who you are, because they want your job, or simply because you're important. This goes double in fiction, where there wouldn't be a plot if someone wasn't after your head. Thus anyone who's anyone needs a bodyguard to watch their back. The problem is, anyone who's anyone in fiction is also able to back it up.
This trope concerns bodyguards who are a lot weaker than their charges. Naturally, while there's often no explanation, it can be justified:
They came with the position, so the authority figure needs to keep them around as a sign of their office, if only for formal ceremonies. This especially applies to younger badasses, whose parents might insist they have protection.
Akira's bodyguards in Ai Ore Love Me follow him around because their sheer size discourages creeps from trying to assaulting their charge. Once a creep evades them, Akira has no choice but to make it clear who needs protection. In fact, all boys at Akira's all-boys school who know how much of a badass he is (and that includes his own bodyguards) are afraid of hitting any Berserk Button of his.
In Detective Conan, an old man protects his late friend's nephew by pretending to be his late friend and having the nephew pose as the bodyguard. In reality, his goal was to be the decoy when one of the family members tries to kill the old man to get a larger inheritance.
In Fullmetal Alchemist, Colonel Badass Roy Mustang is the Flame Alchemist. He can blow up buildings and set fire to just about anything with (literally) a snap of his fingers. He's far and away the most dangerous of the State Alchemists. He has virtually no fears for his own personal safety - not because of this, but because he's entrusted his back to Riza Hawkeye, one of the military's top snipers, who takes her job veryseriously.
There's also Ling and his subjects Fu and Lan Fan, who are his sworn protectors even though he can more than handle himself in a fight (especially once he becomes the second Greed).
Mahou Sensei Negima!'s Kurt Godel shows up with a legion of armored mooks as a personal guard, claiming to have a fragile constitution. When shit goes down, they get knocked around as easily as Faceless Mooks always do, and just when you're ready to see that Irritating Smirk get knocked off his face - it turns out he's basically the setting's most powerful swordsman. Shit.
In Naruto, during the Kage Summit Arc, all five Kages (who are the best shinobi in their villages) pick a couple of guards to go with them. Despite the bodyguards being inferior to the Kages themselves, they are still very badass ninjas in their own right and often possess unique techniques that nobody else has.
Pluto has Epsilon, one of (if not the) most powerful robot in the world being guarded by a somewhat generic security robot. Said robot even remarks the irony of it.
Both the comic and film version of Iron Man has his personal assistant/driver and de facto bodyguard Harold Joseph "Happy" Hogan. Justified somewhat in that Happy is usually guarding Tony Stark while out of the armor (Tony usually has a spare suit of armor in his briefcase anyway) and is still officially his driver.
As a diplomat, Wonder Woman has at least once had a division of Secret Service agents (unpowered people with pistols and radios, mind you, not other Amazons) assigned to protect her. It is hard to imagine a threat they could defeat which would even give her as much as a scratch.
In an Alternate UniverseCaptain America became President of the United States. The secret service agents felt a bit unnecessary, and one commented that he felt safer with the president around.
Sasha Bordeaux from Comicbook/Batman, though badass in her own right, definitely qualifies, seeing as the guy she was hired to protect is Bruce Wayne. This eventually led to her deciding to take additional levels of badass to try to keep up with him once she knew who she was really protecting. It had gotten pretty bad when she was constantly getting ducked by her charge.
In House of M, Rhino probably qualifies as the most useless bodyguard in the world (while serving as Spider-Man's bodyguard when Spidey was on good terms with Magnus).
The eponymous protagonist of Warren Ellis' issue-one-of-a-comic-that-doesn't-exist Simon Spector had a bodyguard, not because he needed one to protect him from threats but because all the fighting styles he knows are fatal.
The /My Little Pony: Friendship Is Magic fan fiction Duel Nature centers around Twilight becoming this for Luna. It's not so much that Luna needs guarding as Celestia is punishing them both for a Wizard Duel that got way, WAY out of hand. Twilight seems to take the responsibility seriously, though.
In Hero, two assassins assault the imperial palace, cutting through a small army to do so. When they reach the emperor, the weaker of the two stays behind to hold off the whole army alone, while the other goes in to duel the emperor in single combat. "The Imperial Guard are not worthy of mention," indeed.
The impressive-looking Imperial guard, who protect the Emperor, a Sith Lord. They're never seen doing anything in the original trilogy and are dispatched within a fight in the prequels.
General Grievous's custom droid bodyguards. Though not quite as strong as Grievous himself, they're still very tough, and often help turn the tide in closely matched fights. Their number justifies the role.
In The Wheel of Time there's the The Maidens Of The Spear, an Amazon Brigade who act as a bodyguard for Rand Al'Thor. As he is The Chosen One and the most powerful channeler (magician) in the world, they can be rather redundant. They guard him in the first place more as a point of honor than anything, since Rand's mother was a Maiden.
In David Drake's Redliners, early on the major has a bodyguard whose sole purpose is to keep the major from doing anything stupid like trying to lead an assault from the front; his job is to lead, not be a badass, though badass he is.
Nobles and landed knights have access to the best training and equipment, making them typically some of the best fighters in the Seven Kingdoms. They'll always have guards at their keeps and will travel with men at arms for protection, even though most are almost surely better armed and trained than the men they command. However this is probably justified as safety in numbers - a single noble warrior, no matter how well trained and equipped and how personally skilled he is, would be vulnerable to getting Zerg Rushed by superior numbers of lesser opponents.
The Kingsguard protect the king, but the king is often pretty badass himself. One notable example is Robert Baratheon, who won the Iron Throne chiefly with his wartime valor. His Kingsguard included some badass veterans, but also a few mediocre knights that he could have wiped the floor with on his coronation.
All Dothraki khals have a group of bloodriders who dedicate the rest of their lives to protecting him. Dothraki khals are typically the most badass fighter of the khalasar, so presumably the khal could kick his bloodriders' asses.
Another example comes with Melissandre, who didn't keep any fear of being attacked, but still had guards about her person to maintain an aura of importance, while thinking about "the trappings of power"
The Dresden Files has John Marcone; an ex-special ops mafia lord capable of taking down all kinds of supernatural nasties without flinching- but his best friend Hendricks works as his bodyguard anyway. Somewhat justified in that if the public knew about his badassery, it'd just be one more proof that he actually does run the Mob, and his life's easier if they're kept in the dark.
The Dresden Files also has the Archive, the living repository of all accumulated written knowledge with incredible magical power and the ability to destroy several millennia-old monsters while being limited to the power in the air around her. And her bodyguard, Kincaid.
Justified because the Archive is a young girl and can't drive herself around.
The Steel Inquisitors from Mistborn are incredibly badass, but their boss the Lord Ruler, who they guard as part of their duties, is far more powerful. Mostly, they're there so he doesn't have to soil his hands with grunt work if he doesn't want to (and as a group they're also in charge of policing his empire, though he's almost always accompanied by a handful). And having Inquisitors is incredibly useful for the times when, to satisfy the Equivalent Exchange aspect of his magic, the Lord Ruler has to regress for a few hours into a withered old man rather an a nigh-invincible Physical God.
In The Eugenics Wars, Gary Seven and Khan are at the South Pole trying to deal with a scientist who's developing technology that allows for control of the atmosphere. They take care of the bodyguard rather easily, but are both overcome by the scientist. It's later revealed that the scientist is immortal and after being everyone from Alexander the Great to Cesar, he's learned to take care of himself.
In Heralds of Valdemar, Monarch's Own Herald is the King or Queen's bodyguard during state functions, even though the current Queen and the Heir can both handle themselves in a fight. Justified because 1) crowned heads leave the fighting to others, and 2) it gives them the advantage if any would-be assassins assume it will be an easy job.
Armsmen tend to be this in Vorkosigan Saga. Some justify this by doubling as a Battle Butler (doing more mundane tasks as well as serving as guards). Also the Armsman might be assigned to protect a dependant, a guest or whatever.
Harry Potter is occasionally given an escort by the Ministry of Magic or the Order of the Phoenix, despite having survived facing Voldemort in five out of five encounters.
The Order does make sense, and Harry gladly accepts their protection (at least until he gets worried they'll be hurt for him), but he does get visibly annoyed when an Auror in a suit tries to manhandle him.
Hagrid acts as this in Deathly Hallows, when he's the one guarding Harry as he leaves Privet Drive. Although he is impervious to many spells due to being a half-giant, as a wizard he's basically a third-year with a broken wand.
Anyone set to guard the eponymous heroine of Honor Harrington (and there's always someone from the third book on) is guaranteed to be less skilled in combat than their Primary. On the other hand, they still make her much safer — by providing strength in numbers, by keeping 100% attention on her safety when she's distracted by other matters, and by making the occasional Heroic Sacrifice in her stead.
Live Action TV
Discussed on Babylon 5: Ta'Lon, a Narn soldier that Captain Sheridan had previously saved, declares his intention to return the favor by protecting Sheridan, whether Sheridan wanted it or not. That said, his own duties prevented him from acting on this intention.
Subverted on Merlin. Arthur is the best swordsman in the Five Kingdoms and can defeat two other swordsmen blindfolded. He has a servant which watches his back on missions. Subverted in that the servant is Merlin, and can kill you with his brain making him the more badass of the two.
In Game Of Thrones, Khal Drogo has bloodriders who protect him even though he shows that he's perfectly capable of killing even his battle commanders at will.
In season 7 of Dexter, Big Bad Isaak Sirko usually goes around with a bodyguard that does nothing other than looking intimidating, as Isaak does all the killing by himself.
One headline from The Onion in 2008 claimed "McCain Vows to Replace Secret Service With His Own Fists." Given that McCain is combat veteran who survived five plane crashes and two years of torture, the gag has some basis.
Warhammer 40000: Space Marine Honor Guards are deployed to protect the Chapter Master, who did not get to his position by being a pushover. Then again, the Honor Guard is basically just an excuse to get as many badasses on the battlefield as possible.
Prior to that, the primarchs and the Emperor had guards of Space Marines and the Adeptus Custodes respectively. Though the Custodes also had the task of handling security, verifying visitors' identities and guarding the castle.
In White Wolf's Street Fighter RPG you could get bodyguards as a perk — it was explained that they were capable of getting people out of the way without hurting them, so a fighter didn't end up getting sued.
In Traveller High Imperial Nobles have Huscarls even though they themselves might well be a badass.
In Dungeons & Dragons, Glass Cannon characters like wizards can deliver extremely powerful attacks, but get a lot of use out of fighters who can run interception on enemies.
Chess: Played with. The pawns start off in front of the far more powerful pieces. The king himself however is not very much of a badass.
Pretty much universal in any RPG.
In Skyrim, early in the main quest you're given the title of "Thane" when it becomes clear that you're a Dragonborn. As a result you're assigned a personal Housecarl named Lydia. Since this is a sandbox RPG this trope is inevitable no matter how powerful she is (although you can give her better equipment to keep her useful). Other companions (including housecarls you can get from other settlements) who're supposed to serve as bodyguards also fall into this.
On the other hand, this can be completely averted if the games' leveling mechanic is properly manipulated. Housecarls' levels are not set until you encounter them for the first time, and some of them do not exist until after they are assigned to you (via completing the necessary quest). There have been tales of players completing quests 30 levels after they were meant to be completed, only to be assigned Housecarls who, among other things, kill entire cities solo after their master stole a single sweetroll (thus angering all the guards), or slaying Ancient Dragons in single combat (while their masters chase butterflies across the countryside).
Galmar is this for Ulfric. Yeah, Galmar is a tough bastard, but he can't blow you across the room by shouting. Ulfric can.
Vega Strike tend to give Escort Missions for superiority fighters. Meaning that, unless your ship is at least equal, the "escorted" gunship lagging behind, if assaulted by a group of typical foes like Space Pirate or Evil Luddite, may wipe out half of them before you can turn back and approach close enough to hit one. Some of these also carry an anti-capship torpedo and may use it, in which case it's wise not to get in close quarters with potential targets until one of them pulverized. Larger pirate groups are more of a challenge, but still weak on the defence. With better equipment than an average escortee, any pirates are complete fodder, but Aera remain so deadly it's not easy to save your own tail — an escortee have a little chance to get away if targetted, and won't use it until he loses it. In both cases the challenge comes from such fighters also leaning toward Glass Cannon sort — they survive by shredding the opponent very quickly and zipping by, and are worse off in crossfire of a strong group.
In Xenoblade Chronicles when the character Melia is introduced she has a contingent of Mook bodyguards to help her track down a monster she's hunting, they all die in the fight but she manages to beat it off and injure it with one big ether attack.
Likewise, much of Reyn's character development deals with him trying to keep his promise to protect Shulk, even as Shulk grows far more powerful than him.
In Yggdra Union, the two dragon knights in Gulcasa's unit serve this role. Despite the fact that he's definitely much more powerful than they are, it turns out that he does actually need them around. As Gulcasa is notoriously bad at minding his physical limits, in the case that he actually winds up collapsing from sickness or exhaustion, the bodyguards can hold off enemies while other allies get him to safety. This actually happens at the end of Chapter 5.
In Fire Emblem your lords (probably fully trained and with unique powerful equipment if level 1) usually have a few escorts including a Crutch Character. It is fully possible for the lord to completely eclipse every bodyguard they get, but they will still have them as backup with the same job.
Frequently, royalty from aligned countries have their personal guard join your fight. Then when the royal joins as well they outstrip their guard.
The Royal Guards in My Little Pony: Friendship Is Magic are just normal ponies guarding two Physical Gods, meaning anything that can hurt the two can easily wipe out the whole group. Possibly justified if you go with the fanon that the Palace of Canterlot is also the primary administrative centre of the Equestrian government, so there's a lot of ministers, civil servants and archived documents that also need to be guarded.
Another reasonable fanon explanation is the guards are there so the Princesses don't have to risk hurting innocent bystanders defending themselves.
In Transformers, Optimus Prime (i.e. one of the most powerful of a race of giant, sapient Humongous Mecha) sometimes has a human military escort.
ReBoot: Super Virus Daemon is usually shown surrounded by her honor guard. They don't do anything besides glaring menacingly and acting as her personal choir, but since she's Nigh Invulnerable and can block a giant robot's fist with one finger, they're probably just for show anyway.
U.S. President Andrew Jackson was attacked by a man wielding two flintlock pistols. When both pistols misfired, it was not his retinue, but the 70-year-old President himself who went crazy on his attacker with his walking stick. Some contemporary accounts describe the President, who was a military commander and infamous duelist, needing to be pulled off of his attacker by his own bodyguards.
The US Secret Service has often served as bodyguards to Presidents who are complete badasses. The examples that immediately spring to mind are John F. Kennedy (war hero), Dwight D. Eisenhower (the guy who beat Hitler), and Theodore Roosevelt (war hero, police commissioner, deputy sheriff, boxer, judo brown belt, explorer, and complete lunatic).
It is not uncommon for boxers, actors specializing in martial arts, MMA fighters, etc. to have bodyguards. In the case of actors, this might be because they really aren't all that good at fighting, for all their flashy moves on camera. Some fighting styles are also fairly one-dimensional, such as boxing, and don't function as the best form of self defense. Many of these celebrities are physically small, so huge muscular types would actually present more of a threat. Of course, the major reason is probably that they have the money to spend, so they'd prefer other people fight off the crazies instead of putting themselves on the line.
Military leaders, even today where Generals can safely conduct wars in a secured bunker, tend to have guards. Even historic badasses like Guan Yu of China, Alexander of Macedonia, Napoleon of France, etc. tend to be surrounded by guards. This is because in the past, leaders would be on the battlefield directing the fight or even leading the charge, and death of an army's general could lead to the whole force disintegrating. Today, with the chain of command, its not such a big problem but having to bring a new guy up to speed might be a costly inconvenience. In short, the bodyguards protect the General so that he can focus on his job of running the war.
Tanks need infantry support when not performing fast deep maneuvers without stopping to engage anything. So the main strength are tanks, but when they can be mired in a fight they are guarded or it ends up with lots of burned-out metal boxes. This arrangement started back with chariots and war elephants: they are either charging or need protection from being mobbed from all sides. In India footmen protecting chariots were called Chakra Rakshaka ("demons of the wheels").
Since Conservation of Ninjutsu doesn't apply in real life, any single person, no matter how badass, is vulnerable to getting Zerg Rushed - overwhelmed by sheer weight of numbers even if individually the attackers are no match for them - after all you can only hit or shoot one person at a time. Safety in numbers applies.