The word "unchallengeable" is correct and usable in written English.
It is an adjective defined as not able to be disputed or questioned. It can be used to describe something that is accepted as fact or truth. Example sentence: His training and experience made his credentials as a doctor unquestioned and unchallengeable.
It would be tanks rolling, unchallenged and unchallengeable, across the desert.
His credentials as the icon of his "country" are now unchallengeable.
It was a world in which everyone was God-fearing and when everything from floods to comets was seen as the inscrutable (and unchallengeable) will of a jealous, stern deity.Yet it was from this unpromising soil that the modern, scientific world-view bloomed.
SINCE his re-election in January, Binyamin Netanyahu, Israel's prime minister, has been unchallenged and seemingly unchallengeable.
It is the belief among defence thinkers especially those not wedded to any particular bureaucratic interest that domestic security risks may be rising at a time when the United States looks virtually unchallengeable overseas.
And will the revolution make America unchallengeable?A system of systemsThe revolution in military affairs revolves around three advances.
It is no secret that the British government had hoped, and its foreign office had expected, that Mr Mugabe would not be the country's unchallengeable new leader.
AK's seemingly unchallengeable grip has even led to some overblown claims that it is heading towards dictatorship.Founded by Ataturk in 1923, the CHP has been out of power for some 15 years.
Germany's merchant and naval fleets were growing rapidly.Today America's position seems similarly unchallengeable.
At two other media firms, Disney and Hollinger International, moguls who thought they were unchallengeable have been brought down albeit for very different reasons.
He held office for a record term of 10 years (1890 1901), unchallengeable but also lucky.
