Interesting premise.

Have you thought about:

A: Putting a face to the curse. The curse is a girl, perhaps shrouded in mist. A good name for this character would be Arai (Greek goddess of curses)

Arai constantly badgers the lead on every Rotten thing he has ever done. So as he journey’s the lead is constantly reminded of key incidences in his life where he did ignoble acts or lied. The final ‘flashback’ is the thing the lead did that got him cursed and began his journey

B: At the end of a journey is a magic pool, which removes curses. If he washes in the pool he will remove his ‘sins’ and Arai will be no more. But he realizes that those mistakes he made were all part of what made him who he is. So the story ends with him choosing not to wash in the pool and he and Arai set out on a new journey.

C: If there must be a final fight, then when he gets cursed, that act of being cursed not only creates Arai, his accuser, but also a demon. The Demon wants do stop the lead from getting to the pool.

So at the end when he reaches the poo he must face his demon and defeat it.

Once he had defeated his demon, that is when the lead gets peace and realizes he doesn’t need to get rid of his curse but learn from them and be stronger for them.
———–
Each ‘sin’ or curse that Arai accuses the lead of, should have a matching good deed.

Arai accuses him of lying, but we find out he lied to save someone’s feelings.

Arai accuses him of stealing but we find his mother was hungry and they had no money.

Arai accuses him of cursing the gods, and that is how is gets cursed with Arai but he didn’t curse that gods for his fate but he curses the gods on behalf of his good mother who passed away.

In conclusion, I don’t think the lead needs a magic sword, he gets cursed by the gods and she (Arai) is there to constantly chastice him for every bad thing he has ever done. But when he defeats his demon he realizes that everyone is flawed and it’s what you do with your flaws that counts.

Just some thoughts.