How does a married fornicator repent, and will he enter Hellfire after his repentance?

It is from the mercy of Allah Almighty that He forgives all sins for whoever repents from them, even if they were polytheism (shirk) or fornication. If a servant repents with sincere repentance, Allah will forgive their misdeeds, and even transform them into good deeds, as stated in His saying, the Most High: (Indeed, Allah forgives all sins). So, whoever's sins are forgiven and transformed into good deeds will not enter Hellfire, unless there remain sins upon him from which he did not repent. In that case, he is under Allah's will, due to His saying, the Most High: (Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills).