For me, it's anything derogatory (to either sex).. For prime example, Young Throats is just revolting. I often go "off" a model immediately if I see her letting herself being degraded like that.
Derogatory also means anything anal.. I dislike anal because it's filthy, but sodomizing is just ugly.
As stated several times already, whacking off at the end. First, I do not like to look at a guy pulling himself, and with a girl/s right there.. WTF?
Two guys doing a chick is OK if she's really into it, but when I see her rub two dicks together during a blow job, or I see two dicks rubbing against each other during a DP.. That is totally camp and they must be gay for sure.
Tattoos and fake tits.
When I think about it, porn is pretty ugly.