1. not questioned, disputed, or opposed
2. not tested or pushed to one’s limits

Examples

• His authority remained unchallenged for decades.
• The champion’s record went unchallenged until last year.
• She accepted the statement unchallenged.
• The team’s dominance was unchallenged in the league.
• He felt unchallenged in his current job and wanted more responsibility.
• The theory stood unchallenged for centuries.
• Her leadership position remained unchallenged by rivals.