This achievement can be earned with the help of a friend (or random player) in a boosting session.
1.) Create an exhibition match and invite another player to the lobby. I recommend being in a chat as well to communicate.
2.) Player One goes first and beats player Two. After each match Player Two will change characters until 6 different ones have been beaten by Player One (who doesn't change from Fulgore).
3.) Switch roles for the next 6 matches and you each have the achievement in 12 quick matches (15-20 minutes or so.)