Will Allah ever forgive a person who has sinned his/her entire life?
In the name of God, the Most Merciful, the Most Forgiving.
Your question: Will God ever forgive a person who has sinned his/her entire life?
Yes, because God Says (interpretation of the meaning):
”Ask Forgiveness of your Lord and then repent to Him. He will send [rain from] the sky upon you in showers and Increase you in strength [added] to your strength.}” [Quran 11: 52]
And those who, when they have committed fahishah (illegal sexual intercourse) or wronged themselves with evil, remember God and ask forgiveness for their sins; — and none can forgive sins but God— and do not persist in what (wrong) they have done, while they know.
For such, the reward is forgiveness from their Lord, and Gardens with rivers flowing underneath (Paradise), wherein they shall abide forever. How excellent is this reward for the doers (who do righteous deeds according to God’s orders).” > [3:135-136]
I’ll provide you a Hadith about your question:
It was narrated that Abu Hurayrah (may God be pleased with him) said:
”I heard the Prophet (peace and blessings of God be upon him) say: “A person committed a sin and said: ‘My Lord, I have sinned; forgive me.’ His Lord said: ‘Is My slave acknowledging that he has a Lord Who forgives sins and punishes for them? I have forgiven My slave.’ Then as much time passed as God willed, then he committed a sin and said, ‘My Lord, I have sinned; forgive me.’ His Lord said: ‘Is My slave acknowledging that he has a Lord Who forgives sins and punishes for them? I have forgiven My slave.’ Then as much time passed as God willed, then he committed a sin and said, ‘My Lord, I have sinned; forgive me.’ His Lord said: ‘Is My slave acknowledging that he has a Lord Who forgives sins and punishes for them? I have forgiven My slave,’ – three times…” [al-Bukhari, Muslim].
Al-Nawawi (may God have mercy on him) included this hadeeth (narration) under the heading:
”Acceptance of repentance from sins even if the sins and repentance happen repeatedly.”
Ibn Rajab al-Hanbali said:
’Umar ibn ‘Abd al-‘Azeez said: O people, whoever commits a sin, let him seek the forgiveness of God and repent, and if he repeats it, let him seek the forgiveness of God and repent, and if he repeats it, let him seek the forgiveness of God and repent, for it is like chains around the neck of man, and doom lies in persisting in it.
What this means is that a person will inevitably commit the sins that it is decreed he will commit, as the Prophet (peace and blessings of God be upon him) said:
”The son of Adam’s share of zina (fornication/adultery) is decreed for him, and he will inevitably come to that…” But God has given him a way out from the sins that he falls into and He erases them by means of repentance and seeking forgiveness. If he does this then he will escape from the evil of sin, but if he persists in his sin he will be doomed.”
It was said to al-Hasan al-Basri:
”Would not any one of us feel ashamed before his Lord to seek forgiveness from his sin then go back to it, then seek forgiveness then go back to it? He said: The shaytan would like you to feel that way; never give up seeking forgiveness. “
Narrated Abu Dharr:
”The Prophet said, Gabriel came to me and gave me the glad tidings that anyone who died without worshiping anything besides Allah would enter Paradise. I asked (Gabriel), ‘Even if he committed theft, and even if he committed illegal sexual intercourse?’ He said, ‘(Yes), even if he committed theft and even if he committed illegal sexual intercourse.” Al-Bukhari, Book 93, Hadith 579)
God, the Exalted, has said:
”O son of Adam, I forgive you as long as you pray to Me and hope for My forgiveness, whatever sins you have committed. O son of ‘Adam, I do not care if your sins reach the height of the heaven, then you ask for my forgiveness, I would forgive you. O son of ‘Adam, if you come to Me with an earth load of sins, and meet Me associating nothing to Me, I would match it with an earthload of forgiveness.”‘ [Tirmidhi]
God also Says:
”And O believers, all of you, repent to Godin order that you may be successful." [Surah An-Noor: 31] Success is when someone gets what he is looking for and is saved from what he is running from.
”O My slaves who have transgressed against themselves (because of sins), do not despair from the mercy of God. Verily, God forgives all sins. Verily, He is All-Forgiving, Most Merciful." [Surah Az-Zumar: 53]
CONCLUSION: He does forgive even if a person committed sins for an entire life but he must ask forgiveness before his end will come but if he dies in a state of believer and died committing sins in his/ her entire life, if God wishes He will forgive him/ her in Hereafter as long as he/ she did not died as a disbeliever by commuting shirk or disbelief.