1: All they submit are previews for Paid Content for their Patreon or other similar sites.
Nothing irks me more than to see a gallery that consists of nothing but cropped images with the Patreon Logo. deviantART is not a free advertisement site, stop using it as such. Also, if you were commissioned by someone and were paid, do not put that behind a paywall. You already received payment on that picture, and to continue to profit off of it afterwards, especially if it contains the customer's intellectual property is beyond greedy and immoral.
2: Getting overly political and forcing your views onto the viewer.
I already have to hear everyone else in my life bitch and moan about politics, i don't want to have it thrown into my face when I am trying to enjoy art.
3: Changing style from good to WTF happened!?
A few artists I use to follow had wonderful art, and then they decided to half ass it and they went from Disney (metaphorically) to mockbuster. I won't name anyone, but there are several that almost come off as completely different artists altogether.
4: Drawing Disgusting subject matter and/or Fetishes
I do not want to see Gore, mutilation, diapers, pee, scat, flatulence or stink. How does anyone find this stuff appealing? I once watched an SFW artist on another site who went NSFW out of the blue by drawing a Lucario getting circumcised and then shoved into a dirty used diaper. I couldn't unfollow fast enough.
5: E-Begging
I understand what it is like to be broke, however I am tired of seeing Artists who continuously complain about it. Stop fiddling around on the computer and get a job. If you spent half as much energy looking for a job as you do writing elaborate posts, you wouldn't be hurting so bad. And the younger artists are the worse offenders about this. Art is not a suitable job outside of a corporate, commercial or industrial environment. There is a reason most of the famous artists in history were born, lived and died broke.