no idea who started it but pretty sure it started around 2020 and this year, don't remember people doing it in 2019
How Did Opposite Cooperation Start?

It started after teams mode first came out
https://www.chess.com/clubs/forum/view/4-player-tactics?page=2#comment-34682710
hint: yellow is @Ne2willdo is red is @Fukadzume (these were top players who'd team when opposite)
I predicted it would become standard, but it took years to actually happen.
https://www.chess.com/clubs/forum/view/4-player-tactics?page=2#comment-34686566

no idea who started it but pretty sure it started around 2020 and this year, don't remember people doing it in 2019
what about 2021?

It has been there since the start, gamers are fast to find the best strategies.
I don’t understand why people aren’t doing 3v1 isn’t that the best strategy?

hint: yellow is @Ne2willdo is red is @Fukadzume (these were top players who'd team when opposite)
Interesting how Ne2willdo changed username (or it was typed incorrectly) and Fukazume got closed for abuse, sometimes I feel like icystun is the only OG player...

@Ne2willdo was a 4PC legend, he later changed his name to BillCooper13 i think. (I never understood that namechanges, "any 2 willy" had such a good name (poker pun, any 2 cards will do)
These things date back to before the archive. We all had lots of accounts, games were not saved, there were no admins or admin-tools.
reminds me of https://www.chess.com/clubs/forum/view/ouch-1
Anyway oppo cooperation was long considered cheating and still is to this day by many lower rated players, it's by far the most discussed and heated topic in 4PC history. No good solutions, winner takes all has helped a bit, making at least the 3way game interesting.
I think a possible solution would be 3 point checkmate with capture the king, making it more like chaturaji where you just have to try to eat as many pieces as possible. Granted it's kindof a different game.

ah, willy is @Bill13Cooper
https://www.chess.com/4-player-chess?t=archive&p=Bill13Cooper&gameType=ffa&daysBack=0-9999

If this is the case, then simply outlaw teams play and start banning people who think FFA spells " Teams " . And why do they cheat ? To make themselves feel better about themselves or their lives. They are sad people who need to be removed so the rest of us can enjoy the game whether we win or lose.

If this is the case, then simply outlaw teams play and start banning people who think FFA spells " Teams " . And why do they cheat ? To make themselves feel better about themselves or their lives. They are sad people who need to be removed so the rest of us can enjoy the game whether we win or lose.
What is FFA without Teams or at least the elements of Teams? Even without opposite cooperation, you still have the 3-Player Solo stage, where you are forced to cooperate with everyone around you, you have idiots ganging up on a higher rated player just for the fun of it, two people taking one person's pieces on the same move is also teaming, if we were to "outlaw teams play and start banning people who think FFA spells 'Teams'", everyone on the server including the admins and you would be banned. Even @spacebar himself would be banned.

ChessMasterGS : Don't be ridiculous. You are oversimplfying this. I am referring to an attack that is coordinated, where they leave pieces of their own left en prise and ignoring their partner's doing the same thing. A hard alliance where they know their pieces are safe from capture by their partner and visa versa. Besides, people who have to play teams do so to hide their own shortcomings in the game. They aren't good enough to play on their own against an equal opponent . Reread the last sentence. Those who HAVE to play teams. As opposed to players who WANT to play teams.

It should be forced by rule to take the pieces of the player opposite you? That's silly, isn't it? You could be forced to play a move that is not in your best interest.
Also, if you ban the "hard alliances" where you must take "free" pieces from the player you're allied with, the best strategy is still to work with the player opposite you, you just have to make sure that you have your pieces protected and don't "threaten" the pieces of your opposite. This is because teaming with your opposite is the best strategy. It's a part of the geometry of the board.
Even if there was a way to remove the natural location of the pieces (there are far more lines of attack on the players to your left and right than the player opposite you), it would still be beneficial to team up and eliminate a side player. A 1/3 chance of winning is much better than a 1/4 chance. This is even more encouraged in high level play where 4th place loses many points, and 2nd and 3rd hardly have their ratings changed at all.

@DoubleSpeedRocks
You don't understand that "playing teams" in FFA is simply the best strategy. It has nothing to do with wanting to play teams or not, it's just about wanting to win! And to win you are forced to play the best strategy, otherwise you do not stand a chance. Granted at lower levels almost no one understands this, but all advanced players adhere to this strategy.
The reason is mainly board geometry, if you can knock out a side player, you're chances to win are good, where as if you remain as the middle man 3-way, you usually end up taking 3rd.
This has been by far the most discussed topic of all time in 4pc, and there just is not a good solution. Banning is ridiculous, a solution must involve changing the rules so that the best strategy is not to team. So far nobody has come up with such rules. Perhaps a game with capture the king and 3-point checkmate (like chaturaji) would help, as that's really just about eating as many pieces as possible, where you do not want anyone else, even your opposite, to make many points. But it's really just a different game, losing all the fun of tactical mating opportunities.

YES, discussed so many times already.
a) yes it's the best strategy, and many weak players are just shocked when victims of that (because not assisted correctly by another weak opp') but they simply don't understand the basics yet (cf. for instance https://www.chess.com/clubs/forum/view/basic-ffa-aspects)
b) yes, it's implied automatically by the geometry of the board,
c) to solve the problem (if we think it's a problem) is NOT easy, because it's extremely difficult to formulate rules that a computer could apply without having marginal situations that any human would find as acceptable but that would match with the criteria, and the opposite is also true.
d) BUT there are some most shockings aspects of the cooperation like assisted checkmates by 2 queens, and there are some solutions that were imagined and proposed, for instance:
https://www.chess.com/clubs/forum/view/ideas-to-prevent-teaming-in-ffa
and https://www.chess.com/clubs/forum/view/a-new-proposal-ffa-solo-ratings-points-system?page=1

The ONLY reason people play teams in FFA IS BECAUSE THEY CAN'T READ. FFA DOES NOT SPELL TEAMS. Illiterate morons with nothing better to do than spoil other people's enjoyment of the game. People who play teams in FFA do so out of a desire for self importance, and their feeling of power they get from downtrodding other players who just want to test their skill and enjoy the experience of a 4 player game. Chess.com is trying to help, they are doing the best they can. Banned players simply open a new account and go right back to ruining other people's games. Support chess.com by turning these people in. Players have no right to deliberately go into FFA to play teams. Don't report someone just because you lost. If 2 players attack you, and leaving their pieces en prise knowing they won't be captured by their partner, then you report. Bullies will always come into FFA to play teams until it isn't worth their while to do so. And please don't ban my BB use, I'm telling the truth, and everyone knows it.
DSR

Lol. We do it because it's the best strategy. Do you want people to deliberately play poor strategies? It's completely within the rules, and nobody has been banned for it.

44, ok if you say so, but the real world begs to differ with you. There are seperate areas for teams. It says FFA , not teams. Stupidity, arrogance or just plain spiteful are the 3 most common reason people go into an area they aren't supposed to be in to do something illegal before they even start. FFA DOES NOT SPELL TEAMS . Take your garbage and dump it someplace else. And I know of 5 people who have been banned from my reporting. So you're not fooling anyone with that remark. You have no need to go into FFA areas. People like you disrupt and damage for their own enjoyment. Go enjoy someplace else.
I see opposite cooperation being discussed in forums dating back to as early as 2017 (the beta of 4PC), who can this concept be attributed to? (And please tell me if they got play-banned for prearranged teaming)