I do not write. I read. Sometimes I criticize. Mostly I read Harry Potter based fanfiction.
What I really hate?
1. Slash, mpreg, abuse fics and similar nonsense. Seriously, what the f*ck is wrong with you? Get some counseling please.
2. Mary Sues. Author self insertions are so sad really. Such special characters by such special authors. Do not bore the reader with your self esteem issues.
3. Obsessive shipping, obsession with pairing and all other situations where who gets to be Harry's girlfriend detracts from the story.
4. Harry has one or more siblings. Boring. Next.
5. Harry has a kewl name like Harrison, Hadrian or Harold. Boring. Next.
6. The obligatory shopping spree. Especially when he gets a megakewl trunk. Boring. Next.
7. Harry gets one of those itemized inheritance lists at Gringotts. With cute little percentages worked in. Heir to House of Deus ex machina. Et cetera. Boring. Next.
8. The use of Gred and Forge to refer to the twins. Boring. Next.
9. The screeching Molly cliche. The woman is perfectly capable of normal speech.
10. Physically abusive Vernon Dursley well into Harry's teen years. It's a fanon exaggeration and rather disturbing when an author uses it. It suggests the author has issues.
11. Calling casting an assortment of nasty or disgusting spells on a group of students 'pranking'. It's just bullying. Even if it's done against those pesky Slytherins. Guilty douchebags should get their wands stuck up their arse, snapped and turned into a portkey to the Acromantula colony.
12. Referring to a spell by its incantation. It is not the Avada Kedavra, it is the killing curse.
13. Atrociously bad grammar. Your versus you're. At least get a competent beta.
14. Inability to properly punctuate dialogue. It's "Let's eat, Harry", Ron said. Instead of "Let's eat Harry", Ron said. What a difference a comma can make.
15. Bad spelling. Especially when misspelling names, incantations or other specific canon words. For example: It's 'Ginevra', not 'Ginerva'.
16. Spellchecker laziness with regards to (near) homonyms. For example: Using 'conscious' when 'conscience' was intended.
17. Harry does the animagus transformation with a bunch of his friends. It's just such a lame plot device.
18. Dumbledore is the Chief Warlock of the Wizengamot, not the Supreme Mugwump. Research.
19. The obsessive need to endow everybody with a middle name.
20. Harry gets an itemized list of all his kewl skills at Gringotts. Boring. Next.
21. Mindless bashing. We all have our preferences, but letting your least favorite character get seriously out of character, just so you can bash them is pathetic and rather boring.
22. Remus or Sirius addresses Harry as "cub" or "pup". I really wish to reach into my screen, grab the author and repeatedly slap him/her with a medium sized fish whenever this happens.
23. A bit redundant, as it has more or less been covered by number 15, but it really irks me when an author is incapable of spelling 'rogue' correctly and uses 'rouge' instead. I associate rouge with make-up. Receive ten fish slaps and bow your head in shame.
24. Harry has a sensei. No he doesn't. And if he does, the author gets thrown into an "Ooooooooooh! Aren't you the interesting and original one?!" hell of my specific design.