Batman: Arkham Origins

All of the online achievements in this game can be done in Private Matches. The multiplayer side of the game is on Disc 2 of the Retail copy of the game. No downloading or installation is required.

[]This achievement has to be done in the Invisible Predator Online game mode. You will not get this achievement in the Hunter, Hunted game mode.

Lobby Setup

For this achievement you will need a total of 8 players including yourself. You cannot do this achievement with a smaller group. If you have dummy accounts, that might be a recommendation to ease the congestion.

Whoever is the host needs to go into "Create Private Game" from the Main Menu and make sure Mode is Inv Pred Online (Invisible Predator Online) and the recommended map is Chemical Plant. Keep "Map Rotation" Off and then click "Start Game".

Here you need to use your and invite your group into the game until it is full with 8 people. Once you have 8 people you can start the match. If anyone get's disconnected during the match, the match will continue but they cannot return to the game as invites will be disabled.

Boosting Method

I recommend you work on this achievement as soon as possible. In Invisible Predator Online the whole team has 30 lives with the exception of the Heroes. Everyone will be placed in 3 different teams. 3 will be on the Joker Team. 3 will be on the Bane Team and 2 will be on the Heroes Team (Batman & Robin).
Anyone can go for this achievement at the same time. The achievement will not unlock however until the end of the match on the results screen.

Everyone needs to meet up somewhere on the map and then decide who is going to go for the achievement first. Once decided get that person to kill everyone at least once in the match. Make sure to take note of who you have killed to avoid missing someone. Meet up again in the same spot and rinse and repeat until everyone has successfully attempted in getting the achievement. When the match is done, the achievement should pop at the results screen. If not simply try it again by getting the host to restart the match from the lobby menu.

Credit towards my friend tornprince2012, there is a method that can be applied of you want to have certain people on certain teams before your match loads up. This applies throughout the multiplayer of the game.

From the main menu, if you go to "Options" and then select "Game Options" you should be given the option to choose your "Faction Preference". Originally it says None, but you can change this to either "Joker" or "Bane" so that you have a high chance in joining either of the two teams you wish to be on. If you are wanting to be "Batman/Robin", simply keep this as None and choose "Hero Opt-Out" as "No". Get everyone else to choose "Yes" and this will give you a high chance in becoming "Batman/Robin" for the round you are playing on. However even though you have chosen these team members doesn't 100% guarantee you will be on that team. In addition at the end of the round, people can still "Opt Out" & "Opt In" if they want to become "Batman/Robin".

Good Luck!

I found it easier to do this as a bane or joker henchman, although it is possible to be a hero. Usually killing all the other henchman on the opposing side is the easier part, as they can't hide as well and are more aggressive. The hardest part is the heroes. Watch the sky, the rooftops, and if when using your goggles you see one taking out either a friend or opponent out, run there as soon as possible and kill them. It's easier to remember which hero you've killed, and then focus your attention on finding the other. There is no super easy trick, you just have to keep playing your best and eventually you will get it. As a hero, don't focus on taking out just joker or just bane, but try taking out one bane, then joker, then bane again. Once more, just keep trying and eventually it will pop