The definition for "Genocide" is "The deliberate and systematic destruction of an entire people who belong to one group of any kind," or quite simply the hunting down and elimination of anyone in a certain group. This flag works in a similar fashion.
The Genocide flag is a flag which kills an entire team that the shot hits with the exception of rogues. Therefore a rabbit in Rabbit Chase with genocide is very dangerous. Rogues can experience the same reaction with the help of the RogueGenocide plug-in. The flag can be disastrous if it hits the same team, but can be the turning point of a battle, giving you and your team time to maneuver. Genocide is usually, in gameplay, referred simply to as "Geno".
Because a single hit from a Genocide flag wipes out an entire team, the amount of points you get
is equal to the amount of players on that team. For example, if you were to shoot a blue tank with the Genocide flag, and there were four blue team members, you would get four points. However, if you were also a blue tank, four points would get taken away, so be careful!
-Added more, G2U