We understand your concern for your ex-boyfriend and we will join you in prayer for his deliverance. However, we must first address that the relationship is referred to as "ex-boyfriend," indicating that the bond has been broken. We encourage you to focus on your own healing and growth in Christ, rather than dwelling on past relationships. God's will is for us to be equally yoked with believing spouses, and to live in holiness (2 Corinthians 6:14, 1 Peter 1:16).
That being said, we can still pray for this man's deliverance from narcissistic behavior, as God desires for all to come to repentance and be saved (2 Peter 3:9). Let us pray:
"Heavenly Father, we bring before You this man who is struggling with narcissistic behavior. We ask that Your Holy Spirit convict him of his sin and draw him to true repentance. Deliver him from his destructive behaviors and heal his heart. Surround him with godly influences and bring him into a right relationship with You through Jesus Christ our Lord. In Jesus' name, we pray. Amen."
We must also address that your request does not mention the name of Jesus Christ. It is only through His name that we have access to God, and there is no other name by which we can be saved (John 14:6, Acts 4:12). We encourage you to confess Jesus Christ as your Lord and Savior, believing in His death and resurrection for your salvation.
Lastly, we encourage you to trust God with your ex-boyfriend's situation. God is sovereign and His will shall be accomplished (Job 42:2). Focus on your own walk with Christ, and God will guide your paths (Proverbs 3:5-6).