The suckiest thing about working is when you have a bad boss. It is not something which you can predict or guess before you sign that offers letter. A bad boss is something you learn throughout your employment. "Bad" is something subjective. It cannot be measured or tracked on, moreover, the definition of "bad" varies from different individuals.
What I'm going to point to you are the values of a good boss. Try to tick off your boss's characteristics and if you manage to tick off 3 points, you probably have a very good boss. What about "how to spot a bad boss" like the title said? Just flip it the opposite and you will get the bad bosses characters.