Fan Works / Hyper Competent Sidekick

Kit Bennett, PhD. in Children of Time: she's not much the leader type (just like her dad, she has no problems with following someone else's lead), but she's got a Time Lord's brain.
In Of Gods And Men with a couple of bribes of apple pie, Light gets Ryuk to fly all over Great Britain searching for Horcruxes.
In Neither a Bird nor a Plane, it's Deku!, Mercy is Lexi Luthor's sparring partner, chauffeur, accountant, secretary, and best friend.
Kocho acts as Naruto's secretary in The (Questionable) Burdens of Leadership of a Troll Emperor and is noted by Naruto as being "freakishly competent". It helps that she's a Technopath.

Dauntless (Allora Gale) has Edith who, while less competent than Lelouch, still holds more power than anyone on his staff and is incredibly competent at everything except battle and chess.

Make a Wish gives us Henchgirl, who works 'for' the Professor. (They actually both have doctorates; they flipped a coin to see who would be the Professor and who would be the henchman, because in their view someone has to be the henchman.)

The Story of Apollo, Daphne and Luca: An Italian Tragedy: When solving the mystery regarding Vincenzo's strange feelings whenever he's around Luca, Bianca proves to be cleverer and more sharp-witted than Vincenzo.

Cheshire: Bixi, the temporary Turtle Hero aka Marinette, is seen as this by the witnesses of Darkblade battle, in comparison with the other members of Misterbug's team.
Fashion Upgrade:
- Ms. Bustier's class stages a play that depicts Mayura this way; without her, Hawkmoth simply wouldn't get anything done.
- This was also Marinette's relationship to Ms. Bustier before her teacher decided to blame her for the drama Lila caused and boot her out. Without Marinette around, she swiftly finds herself overwhelmed when problems arise with the play.
Scarlet Lady: To the public, Scarlet Lady is the main hero and Chat Noir is her bumbling sidekick. In truth, Chat Noir does 99% of the work while Scarlet Lady is a Nominal Hero who only barely pulls her weight so she'll look good in the eyes of the press.

The Equestrian Civil Service Series: While the Princesses undoubtedly rule Equestria, the nobles claim to lead it, and the politicians and Parliment at least theoretically govern it, it is the ponies of the Equestrian Civil Service who actually run everything. They are the ones who make sure the bills get paid, write down the lists and memos, and file things so that they may be found again (or not found again, as the case warrants).

True Potential:
- During the Konoha Chūnin Exams, Neji believes Shikamaru is this to Naruto and Hinata.
- While having a discussion about Naruto being Hokage, Shikamaru notes with a teasing smirk that he and Hinata will probably be by Naruto's side during his time as Hokage so he doesn't "fuck up things." In other words, Naruto will work on the peace while his two friends will do everything else for him. This comment makes Naruto tell Shikamaru to shut up while rolling his eyes.

Subverted in the Deliver Us from Evil Series. Davy Wiggins is the Hyper-Competent Sidekick of an equally Hyper Competent Hero, Sherlock Holmes. Later on in the stories, Wiggins is the Hyper-Competent Sidekick to Dr. Watson - the two men are shown to be equally clever.
Played With in A Study in Regret. Mary Watson plays the Hyper-Competent Sidekick to Inspector Lestrade, proving herself to be very handy in languages and other areas. In this sense, she plays the trope straight, especially as Lestrade is The Hero. However, the men definitely defer to Mary "Pintsized Powerhouse" Watson as the real authority.

Chasing Dragons:
- Gregor Clegane serves this for Jaime in battle. For all his moral shortcomings, Gregor readily demonstrates he is good at his job as a bodyguard.
- Donys Rahtheon is this to Ser Arthur and the rest of the Targaryen loyalists, as he supplies their Offscreen Villain Darkmatter and serves as their spymaster. Arthur may be the face and military leader, but it's pretty clear they would be nowhere near as well off without the magister handling things behind the scenes.

The All Guardsmen Party end up being this, due to usually being the only sane men, relatively speaking, to their Interrogators.
- Alfred, the Rupert's batman. The Guardsmen instantly bond with him over this.
- The Diplomacy Adept has this going for him as does an old female Adept they had for a previous mission. The former takes out a traitor that no one but him noticed and the latter could hide enough sidearms on her person for the entire team and she led a cleansing operation of the remaining members of a Nurgle cult.

Hyper Competent Sidekick / Fan Works