Has both single and multiplayer game modes but was made with clear focus on multiplayer. Singleplayer is possibly exactly same as multiplayer but with the other player characters controlled by bots.
The first video game about Multiplayer focus was released in 1980.
These games tend to have very poor AI, at least for the cases where you don't fight against bots in multiplayer.
These are possibly much harder to play solo too, as some mechanic that is possible with other players is missing (e.g. resuscitation).
* Multiplayer only