"leave unchallenged" is correct and usable in written English.
It means to not question or dispute something. Example: The lawyer's argument was so convincing that the judge left it unchallenged.
But I cannot leave unchallenged his implication that literary study has turned into a dull, pallid discipline.
How can it be right for those of us who believe in liberal democracy to leave unchallenged those who would discriminate against religious minorities, women, homosexuals and Muslims with dissenting or heterodox views?
"Britain can no longer afford to leave unchallenged the recent examples of craven Kremlin apologism in UK politics, particularly given anxiety over how Nato will hold together with Donald Trump as US president.
That would leave unchallenged the main thrust of a legal assault by the State of Idaho and Boise Cascade, the timber giant, which are seeking to overturn the policy.
Every lie and illogical frame that we leave unchallenged takes its place in The Narrative what people see and hear.
Why does an NPR host leave unchallenged an Israeli scholar's assertion that Palestinian casualties aren't excessive because "so far well over three quarters have been armed gunmen, and that is a percentage which is very rarely attained in urban warfare"?
