I have a PC who is playing as a level 14 hulking hurler who throws rocks that deal 40d6+34 damage [deals 171, 173, and 179 for an example] and is confused when people are thinking that he might be slightly overpowered. He then complains when the wizard he was fighting that witnessed his feats of damage immediately turned greater invisible and began flying, casting spells on him [ray of stupidity] and eventually becoming comatose [for reference, I have the spells set up before sessions start so I don't 'fudge' the spells that they have to make things harder/easier] and demands the CR of the enemy be raised by three. [This took place in a 2v2 arena where him and a rogue was up against 2 wizards and he threw a boulder, killing one instantly].
My bet is to have his adversaries try to cast a spell to ruin his boulders or disable his phoenix cloak, or get rid of his automatically-sizing returning bowling ball, but I need advice with how to go through with any of this. Should I just tell him that he might be too op, he just got the ability to deal this damage, but still, he deals on average 174 damage per throw with his returning bowling ball.