The opposite of un-grudging can be described as reluctant, begrudging, unyielding, or ungenerous. A begrudging person is someone unwilling to give or share, often showing envy or resentment towards others. A reluctant individual is hesitant or disinclined to act or express oneself freely. Unyielding denotes inflexibility or a resistance to compromise. Someone who is ungenerous is unwilling to give, even when they have more than enough to spare. While un-grudging involves generosity and a willingness to give without reservation, its antonyms suggest a lack of generosity, stubbornness, or miserliness.