Meaning of "best among the worst"

What does best among the worst mean? For example, if a person is best among the worst does it mean that he is the worst of all or that he is a good person in a group of bad persons?

It means that such a person is the best of a bad bunch.

The best among the worst literally means what it says. If a person is the best among the worst it means he has the most good qualities among the group of people with the least good qualities.

Your doubt is very understandable. It is easy to interpret the phrase as 'superlatively worst' as you have, though incorrectly, suspected.

Here, worst is not an adjective but a noun and therefore could take best as an enhancer. However, it does not. So phrase does not mean 'superlatively worst'.

It simply means that he is the best among the group of people, the group being the worst of all.