Antonyms of adj unchallenged

1 sense of unchallenged

Sense 1
undisputed, unchallenged, unquestioned -- (generally agreed upon; not subject to dispute; "the undisputed fact")

INDIRECT (VIA uncontroversial) -> controversial -- (marked by or capable of arousing controversy; "the issue of the death penalty is highly controversial"; "Rushdie's controversial book"; "a controversial decision on affirmative action")

Similarity of adj unchallenged

1 sense of unchallenged

Sense 1
undisputed, unchallenged, unquestioned -- (generally agreed upon; not subject to dispute; "the undisputed fact")
       => uncontroversial (vs. controversial), noncontroversial -- (not likely to arouse controversy)