Balancing PVP Games is a very complicated issue. The Idea is very simple: give each player the same chance to win. In practice it is not easy. Due to the type of game, there are two types of games: symmetric and asymmetric.
Symmetric games are those in which each party, at the beginning of the game has the same resources, situation and chance of winning. This type of game is easy to balance, as it is enough to take care of the symmetric of the game.
An example of such a game can be chess. Both players have the same figure in the same position. However, this is a turn-based game that has a very important drawback, which is probably impossible to avoid. This problem is the first move. The statistics show that the person who performs the first movement in chess has a większeszanse win. This Problem can be attempted to compensate. In the game Heartstone (this is not usually a symmetric game, but worth mentioning) this problem was solved by giving the second player a card, which increases his mana resource. Statistics show that this is not the perfect solution, as those with the first movement win 52% of the games.
The first traffic issue does not exist in real-time games. An example of such a game can be any game FPS, in which all players start with the same weapons, the amount of life, and what is important on a symmetrical map, which does not give any of the players an advantage.
Asymmetrical games are where players have different abilities, paths to choose from, or initial states. For example, let us use the recently mentioned game Heroes of the Storm. We have two teams equal to numbers, but usually have different characters in their composition. Balancing such a game is extremely difficult than the symmetric game. The designer must take into account many more factors, HP, speed, damage, skills, and even opportunities to co-figure. It is not possible to accurately predict the chances of winning each character without carrying out appropriate tests. Character balancing is largely based on statistics, where a large sample of the results is taken. When a character achieves better results, it has to be weakened and the latter having weaker results strengthened. Because of this diversity, I do not think it is possible to make a perfect balance of such a game. This is reflected in the changes in each patch.
Another factor issuing that the game can be asymmetric is the map. Players can have equal initial conditions, but their location in the world is much better. Such a advantage may be the proximity of resources in RTS games or proximity to weapons FPS games.
Another aspect that is indirectly related to the balance. This is the ability to catch a player who has gained an advantage during the initial stage of the game. A player who has coped poorly at the beginning of the game must be able to equate with his rival in a later game. Depriving him of this possibility will make the game considered unfair. An extreme example is the game circle and Cross, where the player who performs the first movement has a dominant position to the end of the game. To a lesser extent, the problem was seen in Unreal Tournament 99, where the player, the longer survivors had a greater chance of gaining some improvements that gave him a great advantage.
Another thing is the randomness of the game. If there is an element of randomness in the game, it cannot dominate the gameplay. The player must feel that his high skills give him an advantage over other players who do not possess such skills. An extreme example is the board games for Children "ladders", where the gameplay is completely random. Older players see this and are not such a game of interest. The game's randomness syndrome has even gained its title: The RNG from the English words random Number Generator. In the game World of tanks Sami authors have this thread and created a series of Filmikach, which reveals some unusual situations based on the randomness of the game.
In asymmetric games, there may also be a problem with the dominant strategy, which is the best chance to win. This is an obvious problem with balancing the game, because people who have met this strategy to increase their chances will certainly use it. For example, you can use Diune2, where the only legitimate strategy was to flood the enemy with a lot of tanks. Avoiding this problem is very difficult. The chances of having it solved are only in observing the players (especially the advanced ones) and checking how they play.
Finally, an example of a completely badly balanced game: