To achieve this trophy is required to win four showdown matches in a row.
it's easier than anyone may though in the beginning.
That's what you need to do:
1) You need four players;
2) Split up in two team inviting one of the player in you're game, (at this stage you need to deicide which team get the four win in a row first, then the other team get the four win streak);
3) Launch the search for a showdown match at same time;
4) Get paired up in the same showdown match, (this one will require some tries to be in the same match).
Once paired up in the same match it's done. Play the match, at the end the system will start a new one with the same two team. At this point all you need to do is play 8 game. Four win per team and all the players get the trophy.