Utterly incompetent. Incapable of returning any phone class, and I once had to call them six times in a single day in order to elicit a response to a simple query. The provided the absolute bare minimum of repairs. Mold in our bathroom was simply painted over, and all work was only superficial. Never gave any notice of when they would be coming around to the flat, and were rude in person.
What agent could do to change your mind?
Better communication, actually return phone calls. Give notice of when they were coming to see the flat. Perform proper repairs. Basically all the normal things that you would expect from a decent and engaged landlord.