Famous/infamous
So very, very different.
Y’all. Seriously. These two words are pretty much opposites. Famous and infamous are not synonyms.
How I wish a couple of editors had known this back in the day when they changed my phrasing of “So & So is famous for blahblah something” to “infamous for blahblah.” (Yes, it happened more than once.)
Famous: Popular; well-known.
Infamous: Having a bad reputation; disgraceful.
This is why God invented dictionaries. Or somebody did, anyway. Look up a word to see what its definition is. My favorite is Merriam-Webster.com (m-w.com). Or the plain-old, regular, intuitive, easy-to-remember dictionary.com.