I made tawbah years ago, but something I wrote and shared back then is still out there, still being passed around. I have stopped, yet the harm has not. How can my repentance be complete while my old sin is still spreading without me?

You stopped, and the harm did not. Both of those are true, and only one of them was ever in your hands. The ache you still feel after all these years is not the sin left over in you, it is the tawbah still working. Allah did not give you that ache to punish you with it. He gave it to move you. And notice what He does with a heart that turns back: He does not only wipe the page clean, He writes something else in its place.

“Except for those who repent, believe and do righteous work. For them Allah will replace their evil deeds with good. And ever is Allah Forgiving and Merciful.”

Qur’an, Al-Furqan 25:70 · meaning

Read that slowly. Not cancelled, not merely pardoned. Replaced. The deed that keeps you awake tonight is the very material Allah has offered to turn in your favour. Undoing the past was never your task, because that was not given to anyone. Your task is to keep walking in the direction repentance turned you toward, and to leave the turning of the past to the One who alone can do it.

“And establish prayer at the two ends of the day and at the approach of the night. Indeed, good deeds do away with misdeeds. That is a reminder for those who remember.”

Qur’an, Hud 11:114 · meaning

So keep the remedy simple and near. Do what your own two hands can honestly reach, and no more. Where the old writing can still be taken down, ask for it to be taken down, quietly and without any drama. Say once, plainly, in the same place you once spoke, that you no longer stand where you stood. Reach the few people you can still name. Then stop counting, because what travelled beyond your hand was never written in your account to begin with.

“Have taqwa of Allah wherever you are, and follow an evil deed with a good one, it will wipe it out, and treat people with good character.”

The Prophet (peace be upon him), Jami’ at-Tirmidhi (1987) · meaning

And here is the part with the most hope in it. If a harm can travel without you, so can a good. Do not spend the rest of your life chasing old sentences into every corner of the earth. Put something better on the road instead, something that keeps walking long after you are tired. One true sentence. A benefit that others pass on. A student helped, a book that keeps changing hands, a small charity that keeps giving while you sleep. Let the good outrun the regret.

“He who introduced some good practice in Islam which was followed after him, there would be reward for him like the reward of one who followed it, without their rewards being diminished in any respect.”

The Prophet (peace be upon him), Sahih Muslim (1017e) · meaning

Then in the last part of the night, when the house has gone quiet, raise your hands for the people those old words reached. You cannot find them. He can. Ask that whoever lost something be given better than they lost, and that your name sit lightly on their record. Dua travels further than any link, and it reaches addresses no search can find.

Your tawbah is not waiting for the internet to cooperate. It was accepted the moment you turned, and it stands for as long as your face stays toward Him. What is left in front of you is not a debt you are failing to pay. It is a field put into your hands, and there is a lot of daylight left to plant it.

One small step: Tonight, before you sleep, do the one reachable thing about the old writing, then set one small good running in its place, and hand the rest to the Most Merciful.