I let a flat for about 6 years and had very few problems. Most of my tenants were well behaved and elft the flat in good condition.
The worst were a couple of Irish new graduates who, quite simply had no domestic skills or knowledge. An (irish) friend told me that Irish mammies ran round their sons as if they were little gods, and they never did anything for themselves - these lads were born in the early 1980s, and things may have changed.
None of the damage was deliberate, and none of the dirt was offensive. They just did not have a clue. Duvets were damaged because they were slow getting bedlinen, lampshades were resting on the wrong light bulbs and had holes burnt in them. They only ever hoovered the centre of the room, they left the grill on all one night and melted all the knobs that operated the burners on the hob. This event also, as I discovered, after we had signed everything off, damaged the electricity consumer unit, which cost over £500 to replace.
However that one disastrous year apart, most of my tenants were excellent and we became good friends with the last ones before I sold.