In the lake of fire, you would wish one sin less. It would be tremendous relief from the searing agony that will be eating up your body and soul.
How you would wish to be allowed to go back in time to undo just one sin. It would be an immense favor like going out of hell itself. Every single sin would feel like it's the only one sin that did you in there. It would seem like it's the only one sin that caused you to suffer there forever and ever. But then, alas! the reality is, there are so much more and it's eternally too late.
There, you will realize that EVERY. SINGLE. SIN. MATTERS. Every single sin, every single transgression and every single iniquity will come back to you to haunt for all eternity. Those that you have forgotten you are destined to remember.
You only live once, all the rest is an entire eternity of facing up to what you've done.
On that Day, you would wish that you had taken sin seriously and heeded this message---Repent and turn to the Lord Jesus Christ, trusting in Him and what He did on the cross for your salvation.