The characters were always swearing in Japanese scripts/subtitles. Like Leon's "These fucking women" line from BIO2 (OG).
I dont think they say the " f " word in japanese though. In rerev2's japanese script, moira says something like " This is bad. " a lot but in english, this gets replaced with " f " word quite often.
Like for rerev2 as an instance...
English: "What in the moist barrel of fucks-"
Japanese: *Distressed* "What is this place?"
English: "Fucking technology!"
Japanese: "Ugh, this is the worst."
English: "Fucking Barry! All he ever does is push back-"
Japanese: "Barry is the worst. He's always-"