To earn this trophy that's called "On The Edge of Your Seat," all you have to do is play Spectator Mode.
This is another easy trophy to get! From the main menu, you need to first select the Extras option, followed by the Spectator Mode option. Next, make sure it's COM VS Com in a solo match, Choose two characters, then choose the stage, and let the match load up. Once it does, the trophy should unlock shortly afterwards!
Have fun and good luck!