Failure to properly address maintenance requests in a timely manner. In my current apartment:

• I’ve had one plumbing leak cause my ceiling to come down, that took more than a month to get addressed.
• I’ve had another leak in the bathtub that spilled enough water on the floor to saturate beach towels for 72+ hours, that took a week and a half to address (all the while my apartment was technically uninhabitable).
• I can see daylight through the corner of my front door, the hole the daylight is coming through is big enough I have lizards coming in. That’s been an open and continuously reported issue since April.
• Leaky window reported in late August/early September, still hasn’t been looked at, let alone repaired.
• garbage disposal had no gasket in the drain from the sink (i.e. you could clearly see the blades), reported in April, not fixed until July