In PvP MMO, you can duel with other players or gather a team to fight with the enemy squad. PvP battles are much more diverse than PvE because people are very cunning and inventive in their desire to have fun. For example, in PvP MMOs, the big fun for the high-level players is to hunt newbies who are just starting to play.
Also, the developers often enter into the MMO a game the two or more warring factions. Players usually pick up this idea and begin to fuel conflict between adherents of different ideologies. It gives rise to many clashes and huge battles faction x faction.
In many PvP games, you can also unite in guilds and clans that led by real persons. It is not surprising that many of them compete for owning some in-game privileges, such as clan lands or capturing castles. It brings new colours to PvP. Guild-to-Guild battles are striking in their scope and dynamism, and the intelligence of siege strategies will be envied even by real military generals.
DayZ is a survival game, where your most terrible enemies are not zombies, but people. You can team up with other players to survive together, build and defend your settlement, or kill and take their things, invade other people's bases and rob them. Never believe the person who writes "friendly" to the chat.
World of Warcraft is a game, where the confrontation of two factions became known even outside the game world. When you are creating a character, you need to choose whether you will fight for the Alliance or the Horde, and after that, all players of the opposite faction will become mortal enemies for you. Moreover, on PvP servers, a lot of people are hunting on low-level players. Some gamers consider this a challenging complication of the game for beginners, some think it is an annoying and repulsive factor, but the fact is that this activity is viral in Warcraft.
Eternal Magic is one of the games where PvP takes on a colossal scale. It has a wide variety of PvP modes, like massive battles with 80x80 players, Guild Wars, classic combats with game-modes like Domination and Reinforcements, and MOBA mode.