Here is an example of unintentional sins, that God forgives whenever Christians sincerely repent of them:
Paul here - is describing the regular struggle a Christian has against unintentional sins in their lives:
Rom 7:20-25
20 Now if I do that I would not, it is no more I that do it, but sin that dwelleth in me.
21 I find then a law, that, when I would do good, evil is present with me.
22 For I delight in the law of God after the inward man:
23 But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members.
24 O wretched man that I am! who shall deliver me from the body of this death?
25 I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin.
KJV
Heb 13:4
4 Marriage is honourable in all, and the bed undefiled: but whoremongers and adulterers God will judge.
KJV
Rev 21:26-27
26 And they shall bring the glory and honour of the nations into it.
27 And there shall in no wise enter into it any thing that defileth, neither whatsoever worketh abomination, or maketh a lie: but they which are written in the Lamb's book of life
KJV
And here's an example of how God forgives the sins of all those who sincerely repent of their sins:
1 John 1:9-10
9 If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
10 If we say that we have not sinned, we make him a liar, and his word is not in us.
KJV
So there's a huge difference between forgiven sins and unforgiven sins. And between intentional sins and unintentional sins. One example of unintentional sins, commonly is in our thoughts. Our thoughts often displease God. But if we repent sincerely as of other unintentional sins - He always forgives us.