Most of mine have been okay, but thats because it was mainly our small friendship group sharing together.
I guess our worst one was a girl, lets call her Jenny, now none of us were hugely tidy but she was almost a competitive mess maker. If she put something down somewhere it would stay there until she needed it again. At first we started putting things just outside her room, but it made no difference so we stopped. She used to take her socks off on the sofa every night and just leave them there, she would genuinely leave them untip she did laundry (which was rare).
She never cleaned anything, so she would cook in the kitchen and wash any item that belonged to her, but anything else would be left dirty. So she would wash her plate, knife, fork etc, but if she had used someone elses saucepan she would just leave it, she also never cleaned the work surfaces, hob etc.
We had a cleaning rota so everyone had to deep clean a communal area once a week and it had to be done on certain days ideally. She never ever once cleaned any part of any communal area.
She was solitary, which is fine, but she maybe spoke to me 3/4 times in the entire time we lived together. She was a nurse, she worked at a GP surgery rather than a hospital.
Thankfully she moved out after six months, when the landlord came round to check her room it was full of rubbish, anything she had used, crisp packet, potnoodle etc was just strewn in the room. There were even disgarded sanitary products, but my favourite bit (and I remember it well) was a co-op carrier bag full of dirty socks!
The whole situation was odd, we did wonder if she was unwell, but the state of her room when she left confirmed that really.
Apart from her I haven’t really lived with what I would call a bad housemate.