If you say that someone's position of authority is unchallenged, you mean that it is strong and no one tries to replace them. He is the unchallenged leader of the strongest republic. the man who has led his party unchallenged for over thirty years
If you do something unchallenged, nobody stops you and asks you questions, for example about who you are or why you are doing it. I managed to walk around unchallenged for 10 minutes before an alert nurse spotted me
When something goes unchallenged or is unchallenged, people accept it without asking questions about whether it is right or wrong. These views have not gone unchallenged the unchallenged principle of parliamentary sovereignty