What is the expiation for mocking and ridiculing others, what is the way to avoid the punishment resulting from that, and is seeking forgiveness (Istighfar) sufficient?

It is forbidden to mock people, ridicule them, or shame them for a flaw or a sin, as Allah the Almighty says: (O you who have believed, let not a people ridicule [another] people; perhaps they may be better than them; nor let women ridicule [other] women; perhaps they may be better than them. And do not insult one another and do not call each other by [offensive] nicknames. Wretched is the name of disobedience after [one's] faith. And whoever does not repent - then it is those who are the wrongdoers), and as Allah the Almighty says: (Woe to every backbiter, slanderer). The Hadith: "Whoever shames his brother for a sin will not die until he commits it" is not authentic. However, mocking people is forbidden, and there is a fear for the one who does so that they may be deprived of blessings and afflicted with something similar to what they mocked. Repentance from these sins is achieved by seeking forgiveness from those wronged, feeling remorse, and resolving not to return to such acts, along with apologizing and seeking pardon from those who are aware of it, and increasing supplication, seeking forgiveness, and giving charity for those who are not aware.