For me:
Ass to mouth. Fucking disgusting. Do men not think these things through?! Plenty of guys seem to find this hot, but I mean I know the girl's enema'd to fuck, but even so, it's making her suck her shit off your dick. That is fucking rank.
I personally HATE spit. When I see a girl spitting all over a dudes dick it makes me want to gag. It's another thing plenty of guys seem to love or don't care about as much, but seriously, if a girl were just drooling everywhere very few people would think that's hot, but apparently if a dick is nearby? Yeah, drool away! I don't really like seeing guys in porn do the spit on a girls pussy thing. I mean in real life sex sometimes it's necessary and it does create good lube, but watching it in porn just feels gross to me.
I find obviously fake sex sounds in porn really off putting. Probably because I'm a girl I can both tell genuine sex sounds from forced ones and girls tend to be more fussed about things being authentic (in porn/sex situations) than men do. I like noises, but when it's just so fake with zero passion or emotion in the voice (which seems to be most porn), it's a big off putter.
I hate how in so many porn films they have sex, drag it out for ages, try new positions etc, it's starting to get really good towards the end as they finally start letting go and oh wait, the dude pulls out... what for? A blowjob? Oh yeah, passionless head so the dude can cum in the girls face, never seen that one before! This is quite possibly another thing that dudes enjoy, but for me a major turn on is a man cumming inside a girl whether he has a condom on or not, it's the passion and the release into a girls body, it's awesome. Swapping over last minute is about as awkward and unsexy as putting a condom on in the heat of the moment. And although I like cum, on film cum doesn't look as hot as it does in real life, as I am looking from the girls side, as much as I love giving head and I do like to be cum on, it's just not that sexy for me to watch.
I really like anal porn, and one thing I hate is when the girl doesn't look very lubed up. Possibly because I know the importance of lube, it just makes me cringe. I mean I'm sure she is lubed up, but really with anal there should be enough that on film it wouldn't look dry. Surely a dry ass isn't fun for anyone. I also find the whole gaping thing can be pretty weird.
I think a lot of things that I find unattractive are because I'm quite knowledgable in the sex department and I know full well what feels good and actually works in practise and what doesn't. I know good sex and when I see really obviously fake stuff where the girl clearly isn't enjoying herself and the guy doesn't seem to be enjoying it much either it really does put me off, even if they fake in a way that most men would enjoy. A lot of the things that I find off putting are partly because I know what it feels like from the girls side and often go "ouch!" and cringe when watching porn, which is something that I imagine most men wouldn't think so much about. Because pretty much all porn is directed for a male audience it means there are regularly moments where I cringe, though I enjoy porn, it's one of the reasons I tend to stick to my imagination, I swear a lot of porn/searching around for porn leaves me half feeling turned on and half feeling very turned off and a little bit disturbed. It's like they have a super sexy moment and then a really not sexy moment, and then another sex moment, and on it goes!