Complex sentence: Although initially successful Felix's work did not impress the authorities and such was his personality that when criticized he usually resorted to litigation and argument as a result of which he became extremely unpopular and eventually unemployable.
Split into simpler sentences: Although initially successful, Felix's work did not impress the authorities and such was his personality that when criticized he usually resorted to litigation and argument. As a result of this, he became extremely unpopular and eventually unemployable.