How can one forgive the hateful and avoid hatred, taking into account the prophetic Hadith about the hateful and the envious?

Dealing with the hateful and envious is by knowing that they cannot harm except what Allah has decreed, and that they harm themselves, thus one should feel pity for them. Remember that Allah has given them power over you because of your sins, so strive to rectify your shortcomings, and repel evil with what is better, for Allah does not increase a servant who forgives except in honor. As for purifying the heart from envy and hatred, there is no specific supplication for that. Rather, ask Allah for a sound heart and that He purify your heart from these afflictions.