I have my hopes, and they thoroughly betrayed it.
It could have been some gimmick like, a x0 multiplier on one of the enemy stats in exchange of the user's own. And by switching the target between the enemy attack and defense stat simultaneously, he can start chipping away the dragon HP, one tick at a time, and turn this into a war of attrition. To showcase his motivation, personality, desperation, grit, adding in some flashback, and voilà, we have a protagonist. Cliché, you might say, but better than whatever this "underdog got OP skill" we have here.