Does "chief" in the Bible mean worst or most important?

In the Bible, 'chief' denotes the most important or foremost, not the worst or vilest. The context shows Paul was called Mercurius because he was the chief speaker, meaning he was the most important of the two, while Publius is called the chief man of the island, meaning he was the governor or head honcho.

Les teaches that when Scripture calls Paul the 'chief speaker' in Acts 14:12, it does not mean he was the worst, vile, or used awful language. Rather, he was the most important of the two, which is why the pagans called him Mercurius. In Acts 28:7, Publius is called the 'chief man of the island.' Les explains this does not mean Publius was wicked; he was the head honcho, probably the governor, the chief of that island. Les also notes that in Romans 3 the word appears as an adverb, a slightly different Greek form, and he encourages comparing Scripture with Scripture to see the true meaning.

Acts 14:12

And they called Barnabas, Jupiter; and Paul, Mercurius, because he was the chief speaker.

What has happened to the meaning of the word 'chief' in Scripture?

In Scripture, 'chief' means most important, head, or primary, as when Paul was the chief speaker or Publius was the chief man of the island. Its meaning has been twisted to imply something vile, worst, or wicked, which is entirely different from the biblical usage.