Katakura Shigenaga is the first boss during the second main mission called "The One-Eyed Dragon's Castle" of the Dragon of the North DLC.
He is very easy to win BUT in order to get this trophy you have to listen he's dialogue from start to finish before attacking him. The dialogue is not long, just two whole sentences.
So don't worry, Katakura wont attack you before he is finished talking to you. After the talking he will attack you and you will get this trophy.