You see, if someone loves you it does not help you benefit numberless sentient beings or actualize the entire path to enlightenment. So why is this person the most precious thing to me. Because they are angry with you. To you, this person's anger is like a wish-granting jewel. As Bodhicaryavatara mentions, one moment of anger delays realizations for one thousand eons.
Anger is a great obstacle, especially for bodhicitta realizations.
Therefore, because this person is angry towards me, I am able to develop patience and overcome my own anger and complete the entire path to enlightenment. One can complete the two types of merit, cease all the obscurations, achieve enlightenment, and free all sentient beings and lead them to enlightenment.