>>712891845 (OP)Evil doesn't exist but let's assume it does.
The person that struggled has knowledge of how a mind of a single evil person worked and knows of at least one way to fight one's nature which could be applied to others. However, it's not necessarily applicable to others and isn't strictly necessary in order to help others change their ways. A once evil entity probably caused harm to others while one that was always good probably didn't. It is implied the once evil entity is now good but it's not explicitly stated; they might've become something in between.
"Good" is also not well defined.
While overcoming one's nature is commendable, it can be said it's better to be born good. Effort is not, by itself, a virtue.