His disposition towards labour made him endearing to the Manager.

Disposition : an inclination or tendency.
Inclination : a person's natural tendency or urge to act or feel in a particular way; a disposition.
Unwillingness : the quality or state of being unwilling to do something; reluctance.
Temperament : a person's or animal's nature, especially as it permanently affects their behaviour.
Watchfulness : being on the lookout especially for danger or opportunity.

Antonym of Disposition is Unwillingness