i also hate the 'chosen one' stuff, especially if its related to aristocracy or feudalism. its possible to do it well, if characters are aware that the 'choosing' is more or less arbitrary. i thought Dune handled this well by making the destiny/fate a mere generational feudal conspiracy
Dune spoilers that will hopefully be covered in the next movie
the results of which so horrify the protagonist at the time, Paul Atreides, that he burns out his own eyes and wanders the desert as a mad prophet rather than become emperor of the galaxy
also:
-i don't like when gods or deities exist in a literal physical sense, like as a Strong Person with Powerful Body. imo anything like a god should be inhuman and impersonal, normally discorporate unless 'presenting' to humans, difficult to fully comprehend, and more or less uninterested in individual mortal affairs and concerns except in aggregate. Obad-Hai shouldn't just be an old man wandering the woods who can cast powerful spells, the woods ARE obad-hai, the trees and earth are his literal instantiated presence. Fharlanghn isn't just some human wizard walking around on roads doing tricks, the roads ARE fharlanghn, the street lights are his eyes, the pavement his body and prison and definition of form, the movement and flow of traffic his consciousness and thoughts.
-i don't like when magic in fantasy requires overly specific material components, like DnD's insect legs and feathers etc. this kind of thing almost works for slower paced rituals or magical crafting, but a mage during combat whipping out a spider leg to break while they chant and dance just to summon a fireball seems all around less convenient and efficient than making a primitive grenade/petard or rifle/cannon. magic in fantasy or sci fi should upend one's understanding of reality, it shouldn't just be a cheat code activated by arranging garbage and trinkets. a wizard casting a fireball is old hat, passe, boring, a true master of metaphysical arts should make the need to cast fireball irrelevant, locking the enemy in warped spacetime architecture or turning them inside out with a glance and a gesture or instantly transmuting their brain into gold. i want less of the simplistic 'its a weapon attack that uses unique ammo' style of magic attack and more 'my sword has become an incomprehensible fractal of steel and folded spacetime as i try to stab the wizard' or 'the master of secret arts has plucked a beam of sunlight from the sky to use as a blade'. I hate the videogamey trope of 'elemental damage types' and mages-as-bombardiers. the wizard should consider using a sword or bow if they want to just kill people, it doesn't seem worth the violation of causality to do a mere 1d6 damage with a fireball at a mere 50 meters one time when you can likely throw a powder charge farther and for more damage and without manipulating the fabric of reality. instead the wizard should like, teleport in the midst of the opposing army and kill their general with a knife, or less overpoweredly might set his sword to fight on its own accord as if it were held by an invisible man, or illuminate hidden enemies for his allies, or manipulate weather to his advantage. A wizard should be a force-multiplier more than just a better-version-of-a-guy-that-kills-things, a horde of angry drunks clad in steel should always be the best option for 'just killing a bunch of people', a wizard should be doing things that can't be done efficiently with mundane physical means.
-i hate spaceships that have artificial gravity, especially in settings where this technology is mostly unused for any other application (dead space at least gives you a 'stasis module' and 'telekinesis module' that work similarly, whereas Halo simply never explains ship gravity and the humans still use wheels on their vehicles and 5.56 bullets in their guns despite seeming to have better tech available) additionally, i hate spaceships that are overly spacious on the interior, they should be cramped like submarines and it should be impossible to be far enough away from a wall to be stuck free-floating in zero G. The command bridge should never have people standing in it like at a podium like in mass effect, the crew must be strapped into their stations in zero G or maneuvering with safety handles and harness to prevent flying away.
-hover tanks should have to land temporarily to fire accurately, even more stable modern tracked tanks cannot accurately shoot on the move. hovercraft should have helicopter-style landing skids or something similar.
-the taller a mecha is, the longer it's range of combat should be. Mobile Suits should not be sword fighting except when the tactical situation has gone very awry, they have the height to act as a watch-tower and the weaponry size to engage at extreme range, large mecha should basically be using the horizon as cover and making extreme range artillery strike attacks during terrestrial combat. It's ridiculous in the mechwarrior videogames for example to be piloting a 50 or so foot high robot whose gigantic weaponry have less range than a modern infantry assault rifle. the 'long range missiles', the longest range weapon except maybe an ER PPC or ER L Laser, max out at like 900 meters in MW5, while many current day infantry assault rifles have effective ranges of 1500 or more meters. This is a general gripe with all fictitious combat, real warfare in the modern age often means you literally never get a good look at the enemy, mostly shooting at distant silhouettes and movement, whereas in fiction, whether movies or games, the scene must be easily 'readable' and all characters must have an explicit up close presence for the audience.
-additionally mecha should NEVER have their entrance/exit hatch on the front of the torso. In an emergency this will open directly into enemy fire, or worst case you fall on your mech's belly and are stuck. putting the hatch on the top, side, or even the back is a better call, ideally with at least one backup exit.
-most sci fi vehicles should have more than a single crew member. I realize that technology improves over time, but even modern jets often have a separate crewman just for operating the radar equipment while the other flies and controls weapons. for example something the size and resource cost of the Gundam should absolutely never be put in the hands of a single person, AT LEAST put another guy in there as a spotter/support systems operator. it should probably have a direct line to an off-site support staff consisting of military and legal advisors as well.
-Laser weapons should have difficulty with penetration of armor or cover, they heat and explode/melt the surface instead of immediately piercing through. even foliage and leaves should offer temporary cover to lasers until they can burn through.
-i hate when sci-fi appears to grapple with big philosophical topics without really engaging with any specific issues. for example, in the movie The Creator, the message is that the robots are analogous to oppressed people, minorities, and victims of imperialism, but doesn't really engage with any of the actual debates about artificial intelligence. They show robots performing religion as if to say that this makes them more genuinely human, when to me it just says that they accurately mimic our behavior. they could have easily established some kind of specific sci-fi technology to justify this attitude (like Isaac Asimov's positronic brian) but instead they simply do not engage with the ideas at issue in any way and focus on the immediate story and characters with their presuppositions of robot-personhood in mind.