Is it permissible to pray for divorce upon someone who abandoned me after a 9-year relationship and married someone else, knowing that I had already prayed to God to show me the wonders of His power concerning his injustice towards me?

Dating between young men and women and romantic relationships between them are a gateway to evil and corruption. You erred by persisting in that illicit relationship, and you wronged yourself by squandering opportunities for marriage. This young man erred by breaking his promise, but the supplication of the oppressed must not exceed the measure of their oppression. It is not permissible for you to pray for the divorce of his wife. It is more fitting for you to strive in supplication that Allah may grant you repentance and provide you with a righteous husband.