I hate it when a show is initially written as a one-season miniseries, but it's so successful that they decide to cash in and make some more. The vast majority of the time, it's not as good. Sometimes, it's downright infuriating.
That said, I also hate it when a series is based on a great premise that just can't be stretched over multiple seasons, so they pivot to something else instead of wrapping in one season. Take
Prison Break. What did they think was gonna happen after the motherfuckers break out?