Psalm 102's title calls it the prayer of whom?

Answer: One who is afflicted

Its title: "A prayer of one who is afflicted, when he grows faint and pours out his lament before the LORD."

“A prayer of one who is afflicted, when he grows faint and pours out his lament before the LORD. Hear my prayer, O LORD; let my cry for help come before You.”— Psalm 102:1 (BSB)