Fable II’s co-op is utterly unique. You see while the inclusion of a second player, as a rule, can make even a miserable campaign bearable, bringing a quest buddy into Albion actually turns an excellent game into a miserable slog.
Dropping into a friend’s game world, you are a total non-entity. You can’t interact with anything. You can’t flick a switch. You can’t open a door. You can't even start a conversation. You’re totally reliant on the player whose game it is, reducing you to the level of pram-bound sword-baby, as mummy does all of the real, grown up stuff for you. You might as well be a ghost.
Fortunately though, you’re the Sadako kind of ghost, rather than the ineffectual Sixth Sense variety, and should you meet them, one thing you certainly can affect is the longevity of your friend’s in-game spouse and children. By murdering them right up. And they never, ever come back, even after you've left. That'll teach people to ignore you.
Double Dragon
Taito’s 1987 street brawler is one of the most influential games ever made. No, seriously. It introduced continuous side-scrolling to the beat-‘em-up genre, it popularised two-player co-op violence alongside Contra (sorry, current-gen, turns out you didn’t invent it after all), nd most importantly of all, it then immediately introduced Mr. Violent McCo-op to Miss. Gratuitously Dick-your-mates-over-for-fun. They got on famously, and a little while later a whole legacy of bastardly multiplayer was spawned from their union.
How did it work? Simple. Upon reaching the end of the game and rescuing kidnapped love interest Marian, said wayward wench set the victorious Lee brothers about each other in a battle to the death in order to decide which was worthy of her attentions. Thus, the burgeoning fraternal bond of early co-op was drowned at birth.
Left 4 Dead
So there’s a zombie plague going on. As far as you know, there might only be four of you left amongst a great, throbbing, worldwide population of insidious zombie stink. You have only each other to rely on, and the only way any of you will get through alive is if you work as one cohesive, tightly-tactical, co-operative unit. The slightest error from anyone could result in the instantdownfall of the whole team. And doesn’t that knowledge just make it hellishly tempting to balls it all up for everyone?
Above: The still weren't speaking
Of course it does, and in Left 4 Dead there are plenty of fiendish ways to achieve that. You can trigger the climactic Infected horde at the end of stage before anyone else is ready. You can blow things up as your team-mates pass by. You can pull the old trick of repeatedly not-quite-healing a downed compatriot until they go insane. You can direct your friends to a set of pick-ups you’ve found, which in actual fact then turn out to be not so much pick-ups, but more similar to a Special Infected. Probably a Witch. When the smallest error can bring the whole tactical house down, the possibilities for engineering an apocalypse are endless.
Mercenaries
Like Crackdown 2, this is another one where the freedom afforded by the game world can turn co-op into a vindictive playground of creative friend-murder within seconds. Given the vast amount of destructibility in the environments and the proliferation of armed vehicles, there are plenty of ways to ruin your friend’s day.
Above: Life-expectancy of two Mercs in a war zone = a few days. Life-expectancy of partnership = two minutes
Our favourite though, is gratuitous use of helicopter grappling hooks. Wait ‘til your partner is in a vehicle, then pluck him off the ground and abuse him endlessly. The fact that the gunship-carrying-a-tank combo is an accepted Mercs 2 co-op tactic makes this even easier to pull off.
You can drop him in the sea, you can ‘beach’ him on top of a lethally tall tower… Hell, you can even fly lowover the motorway and swing him around, using him as a conker to wipe out the oncoming traffic. Until he explodes. And if all else fails, just drop him in the middle of the suspension bridge and immediately nuke it from the air.
