What should I do to please Allah Almighty and repent to Him after committing the major sin of fornication with a married man, and what should I do regarding the rights of his wife?

Adultery is one of the gravest major sins. The verses of the Quran have made it clear that Allah accepts the repentance of adulterers and transforms their evil deeds into good deeds, provided they repent before the soul reaches the throat, as stated in the words of Allah Almighty: "Except for those who repent, believe and do righteous work. For them Allah will change their evil deeds into good ones. And Allah is ever Forgiving, Merciful." Therefore, the adulterer should conceal their sin with Allah's concealment, sincerely repent, perform abundant good deeds, supplicate for a righteous spouse, and avoid mingling with and being in seclusion with non-mahram (definition) individuals.