Create any one on one match and use a superstar with Poison Mist ability already (eg Papa Shango) or edit the payback ability of any wrestler pre match.
Take enough damage so that both yellow and then red payback meters are filled. When the primary payback meter switches to the red one hold RB and press LB to activate.
You then have a limited amount of time to do the move. Hold and release Y to spray poison mist. NOTE: may take a few attempts