Didn't deliver after having carelessly wasted 3 months of my time.
Hired a designer who disappeared mid-project, having carelessly wasted 3 months of my time, even though at the very beginning, he was made well aware of the consequences that not keeping the timeline has for me as a client.
Additionally, the designer who claimed to have 15 years of experience in UX/UI was not able to tackle even the simplest stuff (while constantly complaining about how difficult the rather simple app was) and after 3 months of cooperation did not have a single screen in a final state, always claiming that "it would be polished at the end of the project". And guess what - it never was.
Eventually, he tried to sell me the "result" for around 75% of the originally negotiated price and told me that I could outsource the rest to a less expensive designer, which to me was a complete joke.
I was smart enough not to pay him up-front, but charging people up-front is their standard process, which I had fortunately refused.
Avoid at all costs, and if for some weird reason you won't, do NOT under any circumstances pay these guys anything up-front.