When translators dont keep the common honorifics in manga but instead localize them.
Yesterday I read the first volume of oshi no ko and they put a small glossary of common words.
But I actually prefer in-line translation notes under the panel or at the bottom of the page with a small asterisk.

Same goes for Anime.

When books, especially scholarly books, don't give the original language version, at least somewhere, of names that they Latinize.

For Manga and Anime in particular:

• Removal of honorifics which convey a person's status which can ba explained in a translators notes page or a quick look at Wikipedia

• Giving people with different dialects from standard Tokyo dialect different English accents like southern americanese or Scottish. They're Japanese, not Scottish or american

• Using american English

• Using american slang which no one outside of america understands

• Even though I don't watch dubs anymore and prefer subs every dub I've seen poorly attempts to imitate the way Japanese people speak

Not infuriating, but I got pretty annoyed by the translator in Shogun constantly changing Anjin’s statements.

When they get pissed off because the publishers/authors decide not to work with them because they want their works to be translated as close to the original while still making sense, so they decide to rant about how it's unfair for themselves to be laid off for ruining works and calling people Nazi's on extwitter for criticizing their bad translations.