unmasterable

listen to the pronunciation of unmasterable
Английский Язык - Турецкий язык
Üstesinden gelinemeyen

One can suggest that the main moral cause of Napoleon’s fall as an emperor was his UNMASTERABLE ambition.

Английский Язык - Английский Язык
Not masterable; that cannot be mastered
{a} not to be subdued or tamed
Incapable of being mastered or subdued