Includes any multiplaeyer mode where one player is against one player with no option of more players regardless of options, map choice, etc.
Name variations: 1 on 1, one on one
The first video game about Multiplayer: One-on-One was released on January 13, 2014.
Messhof has published all these games
One-on-one does not make the versus multiplayer mode tag useless, as this only dictates the limitation of number of players rather than describing the actual game mode.