This trophy is titled "Words Hurt Too" and it's for letting the opponent deal over 5,000 points worth of damage more to you than you have of them and having them taunt you. This is easily rigged with two controllers or another friend, it'd be a bit tougher with the Ai as letting them beat you is no big deal but forcing them to taunt is another story.
When facing another controller/player simply have them weaken you to 1/4 health or so just to be safe, then have the second controller press L1 to taunt. Win the round and repeat if you're trying to earn this for a partner as well. There you have it, a very simple silver trophy!