someone who plays really bad and still wins because of his luck, but thinks he/she is actually good

A tenant who rents out there rented place(s) on Airbnb for profit, thus removing these places from the rental pool.

Landlord who runs basically slums.
Doesn't bother to take care of the plumbing, holes in the walls, floor problems, and the fire escape is to jump off the roof.

A player seen as dirty and/or unfavourable in a game, most often playing outside community rules, or using items and weapons against community standards.

Even worse than a slumlord. A scumlord gives zero fucks to any and all of the tenants (including children) in his building. A scumlord is so greedy and morally absent that he will purposely ignore key safety guidelines and let his own property burn to the ground (with or without the tenants inside) so that he can collect the insurance pay out on the building