Surly staff at check in and on board, insistence on cramming everyone into 3 per row even if the plane is otherwise half empty, the stupid zones system (basically anyone who isn’t in Business gets number 5 and boards last - way to hold up the plane BA, you should be boarding from the back doh), dirty aircraft, laughably extended flight times so they don’t have to pay as much compensation out for properly late flights .. I could go on. Never again.
It would be fewer stars but the flight was cheap because I used some ancient Avios points I acquired years ago.
By the way don’t be fooled into thinking this is a British airline so you should fly with them out of “loyalty.” BA is Spanish.