Zero to Hero: My Sword Path

Grant Jenkins comes down from the mountain on his master's orders to honour a marriage contract with the Nelson family. The Nelsons take him for a useless man who never learned to fight and want the contract gone. Rather than give up their favoured second daughter Joyce, they push the gravely ill eldest daughter Rose out to marry him instead. Grant is an Eighth-Stage Warrior. At the wedding banquet the Nelsons insult him in front of the guests and move to tear the contract up. He stops holding back, and the pressure of an Eighth-Stage cultivator goes through the whole hall, his palm strikes putting down the strongest people in the room. The guests work out that the useless man in front of them has been hiding what he is. Grant stays with Rose after that and turns her situation around.