How long have you got?
More seriously, most of my dislikes have been covered - wonky horizons, overdone processing, brand snobbery,(though I don't see that very often now), gear snobbery, more megapixels must be better, etc.
I'll add -
the opinion that manual exposure is always better. Manual has its place, just like aperture or shutter speed priority,
apologising for posting an HDR photo. No one would dream of apologising for using Lightroom so why apologise for an HDR shot,
and the use of two, IMO very annoying abbreviations/nicknames, -
"togger" and "nifty-fifty"
I don't have much problem with people but probably that is due to my main subjects being landscapes so often the nearest person is a mile away and sometimes much further.
Dave