In case you don't know, I am also a clanmate of djelebert and fairman, so feel free to consider me biased.
You said fairman admitted secret diplomacy, he did not.
The only thing he said in the chat was that yes, he'd rather see djelebert win if he can't, which is not secret diplomacy, and even not saying he would actually act on this wish.
fairman and djelebert have been playing together since 9 years, you cannot expect fairman to not be slightly biased, but he is admitting it because he is an honest player.
Now being biased isn't the same as cheating. True enough, if you can't play without bias, you should not be playing multiplayer game together on a regular basis, that'd indeed be unfair.
Every regular player on CC have person he likes/respect/trust and some of their move might be,
consciouly or not, different when they play against such person that they know compared to another regular player.
But this isn't cheating.
Now, looking at some of the games, I'd say you don't have a case.
For example FuegoFuego is claiming in the chat of this game
Game 20039291that they are teaming up in that one
Game 20039292:
Let's look together at the last 3 rounds
Round 7 :
fairman start, drop 11, attack djelebert ( take 3 regions)
FuegoFuego plays, drop 17, attack both fairman and djelebert - take 4 from djelebert, 5 from fairman
djelebert plays, drop 11, attack FuegoFuego.
Note : with a 17 drop and having taking 9 extra regions, FuegoFuego is clearly leading and therefore it is a very logical move from djelebert to attack FuegoFuego in a 3 player game as it is now that yellow has been eliminated.
2020-06-08 10:54:56 - Incrementing game to round 7
2020-06-08 19:08:09 - fairman received 4 troops for holding 4 Vals
2020-06-08 19:08:09 - fairman received 1 troops for holding FIS AA
2020-06-08 19:08:09 - fairman received 6 troops for 20 regions
2020-06-08 19:08:15 - fairman deployed 11 troops on Montgomery
2020-06-08 19:08:16 - fairman assaulted Wasmuth from Montgomery and conquered it from djelebert
2020-06-08 19:08:19 - fairman assaulted Phelps from Wasmuth and conquered it from djelebert
2020-06-08 19:08:22 - fairman assaulted Avocet from Phelps and conquered it from djelebert
2020-06-08 19:08:26 - fairman ended the turn and got spoils
2020-06-08 23:13:35 - FuegoFuego received 3 troops for holding 2 Kates
2020-06-08 23:13:35 - FuegoFuego received 5 troops for holding Oil Tanks
2020-06-08 23:13:35 - FuegoFuego received 1 troops for holding Oil AA
2020-06-08 23:13:35 - FuegoFuego received 1 troops for holding NY AA
2020-06-08 23:13:35 - FuegoFuego received 7 troops for 23 regions
2020-06-08 23:13:47 - FuegoFuego deployed 17 troops on West Virginia
2020-06-08 23:13:50 - FuegoFuego assaulted Tennessee from West Virginia and conquered it from djelebert
2020-06-08 23:13:55 - FuegoFuego assaulted Arizona from Tennessee and conquered it from djelebert
2020-06-08 23:13:58 - FuegoFuego assaulted Dobbin from Arizona and conquered it from djelebert
2020-06-08 23:14:11 - FuegoFuego assaulted Dewey from Dobbin and conquered it from djelebert
2020-06-08 23:14:16 - FuegoFuego assaulted Phelps from Dewey and conquered it from fairman
2020-06-08 23:14:24 - FuegoFuego assaulted Avocet from Phelps and conquered it from fairman
2020-06-08 23:14:30 - FuegoFuego assaulted Wasmuth from Phelps and conquered it from fairman
2020-06-08 23:14:34 - FuegoFuego assaulted Breese from Wasmuth and conquered it from fairman
2020-06-08 23:14:39 - FuegoFuego assaulted V2 from Breese and conquered it from fairman
2020-06-08 23:14:50 - FuegoFuego ended the turn and got spoils
2020-06-08 23:27:01 - djelebert received 4 troops for holding 4 Zeroes
2020-06-08 23:27:01 - djelebert received 1 troops for holding FIN AA
2020-06-08 23:27:01 - djelebert received 6 troops for 18 regions
2020-06-08 23:27:16 - djelebert deployed 11 troops on Honolulu
2020-06-08 23:27:18 - djelebert assaulted Dry Dock from Honolulu and conquered it from FuegoFuego
2020-06-08 23:27:20 - djelebert assaulted Oil C from Dry Dock and conquered it from FuegoFuego
2020-06-08 23:27:24 - djelebert assaulted Oil AA from Oil C and conquered it from FuegoFuego
2020-06-08 23:27:37 - djelebert ended the turn and got spoils
Round 8
FuegoFuego starts, drop 16. Attack djelebert. ( Start with 29 regions, takes 4 thus 33 regions, will the lose 8 in the turn bringing him to 25 regions)
fairman palys, drop 11, attack FuegoFuego ( start with 18 regions, take 5, thus 23 regions)
djelebert plays drop 9 attack FuegoFuego. (start with 17 regions, take 3 thus 20 regions).
Here agian, FuegoFuego is still the leader, logical move for fairman and djelebert to attack him.
2020-06-08 23:27:37 - Incrementing game to round 8
2020-06-08 23:28:09 - FuegoFuego received 3 troops for holding 2 Vals
2020-06-08 23:28:09 - FuegoFuego received 3 troops for holding 2 Kates
2020-06-08 23:28:09 - FuegoFuego received 1 troops for holding NY AA
2020-06-08 23:28:09 - FuegoFuego received 9 troops for 29 regions
2020-06-08 23:28:15 - FuegoFuego deployed 8 troops on Oil B
2020-06-08 23:28:18 - FuegoFuego deployed 8 troops on Tennessee
2020-06-08 23:28:20 - FuegoFuego assaulted Runway A from Tennessee and conquered it from djelebert
2020-06-08 23:28:23 - FuegoFuego assaulted FIN AA from Runway A and conquered it from djelebert
2020-06-08 23:28:34 - FuegoFuego assaulted Oil C from Oil B and conquered it from djelebert
2020-06-08 23:28:39 - FuegoFuego assaulted Oil AA from Oil C and conquered it from djelebert
2020-06-08 23:28:53 - FuegoFuego ended the turn and got spoils
2020-06-09 07:33:23 - fairman received 4 troops for holding 4 Vals
2020-06-09 07:33:23 - fairman received 1 troops for holding FIS AA
2020-06-09 07:33:23 - fairman received 6 troops for 18 regions
2020-06-09 07:33:39 - fairman deployed 11 troops on San Francisco
2020-06-09 07:33:41 - fairman assaulted Oklahoma from San Francisco and conquered it from FuegoFuego
2020-06-09 07:33:46 - fairman assaulted K6 from Oklahoma and conquered it from FuegoFuego
2020-06-09 07:34:00 - fairman assaulted Oil H from K6 and conquered it from FuegoFuego
2020-06-09 07:34:03 - fairman assaulted West Virginia from Oklahoma and conquered it from FuegoFuego
2020-06-09 07:34:05 - fairman assaulted K4 from West Virginia and conquered it from FuegoFuego
2020-06-09 07:34:13 - fairman reinforced Gamble with 3 troops from Ramsay
2020-06-09 07:34:13 - fairman ended the turn and got spoils
2020-06-09 19:10:54 - djelebert received 4 troops for holding 4 Zeroes
2020-06-09 19:10:54 - djelebert received 5 troops for 17 regions
2020-06-09 19:11:09 - djelebert deployed 9 troops on District HQ
2020-06-09 19:11:13 - djelebert assaulted Navy Yard from District HQ and conquered it from FuegoFuego
2020-06-09 19:11:15 - djelebert assaulted NY AA from Navy Yard and conquered it from FuegoFuego
2020-06-09 19:11:19 - djelebert bombarded V6 from NY AA and annihilated FuegoFuego's troops
2020-06-09 19:11:22 - djelebert ended the turn and got spoils
Round 9
From preivous turn we can know that
(1) FuegoFuego has 25 regions
(2) fairman has 23 regions
(3) djelebert has 19 regions.
fairman plays first, cash and attack FuegoFuego. Still seems pretty fair.
djelebert play 2nd, cash and attack FuegoFuego, there FuegoFUego wasn't leader anymore. you could say this move was questionnable. But with context it may not be.
Also djelebert did take 2 regions from fairman.
FuegoFuego plays take 1 from djelebert, 1 from fairman.
2020-06-09 19:11:22 - Incrementing game to round 9
2020-06-09 21:01:21 - fairman received 4 troops for holding 4 Vals
2020-06-09 21:01:21 - fairman received 3 troops for holding 2 Kates
2020-06-09 21:01:21 - fairman received 1 troops for holding FIS AA
2020-06-09 21:01:21 - fairman received 7 troops for 23 regions
2020-06-09 21:01:30 - fairman played a set of Tennessee, V4, and Oil D worth 15 troops
2020-06-09 21:01:30 - fairman got bonus of 2 troops added to V4
2020-06-09 21:01:32 - fairman deployed 30 troops on Gamble
2020-06-09 21:01:34 - fairman assaulted Breese from Gamble and conquered it from FuegoFuego
2020-06-09 21:01:36 - fairman assaulted V2 from Breese and conquered it from FuegoFuego
2020-06-09 21:01:39 - fairman assaulted Wasmuth from Breese and conquered it from FuegoFuego
2020-06-09 21:01:41 - fairman assaulted Phelps from Wasmuth and conquered it from FuegoFuego
2020-06-09 21:01:43 - fairman assaulted Avocet from Phelps and conquered it from FuegoFuego
2020-06-09 21:01:51 - fairman reinforced UP Hangars with 8 troops from Phelps
2020-06-09 21:01:51 - fairman ended the turn and got spoils
2020-06-10 18:38:46 - djelebert received 4 troops for holding 4 Zeroes
2020-06-10 18:38:46 - djelebert received 1 troops for holding NY AA
2020-06-10 18:38:46 - djelebert received 6 troops for 19 regions
2020-06-10 18:38:49 - djelebert played a set of Runway B, V2, and Z5 worth 20 troops
2020-06-10 18:38:49 - djelebert got bonus of 2 troops added to Runway B
2020-06-10 18:39:04 - djelebert deployed 19 troops on Hangar A
2020-06-10 18:39:17 - djelebert deployed 12 troops on Hangar A
2020-06-10 18:39:26 - djelebert assaulted Runway A from Hangar A and conquered it from FuegoFuego
2020-06-10 18:39:36 - djelebert assaulted FIN AA from Runway A and conquered it from FuegoFuego
2020-06-10 18:39:57 - djelebert assaulted Tennessee from Runway A and conquered it from FuegoFuego
2020-06-10 18:40:02 - djelebert assaulted Arizona from Tennessee and conquered it from FuegoFuego
2020-06-10 18:40:09 - djelebert assaulted Dobbin from Arizona and conquered it from FuegoFuego
2020-06-10 18:40:12 - djelebert assaulted Dewey from Dobbin and conquered it from FuegoFuego
2020-06-10 18:40:18 - djelebert assaulted West Virginia from Tennessee and conquered it from fairman
2020-06-10 18:40:23 - djelebert assaulted Oklahoma from West Virginia and conquered it from fairman
2020-06-10 18:40:29 - djelebert assaulted Maryland from Oklahoma and conquered it from FuegoFuego
2020-06-10 18:40:36 - djelebert assaulted California from Maryland and conquered it from FuegoFuego
2020-06-10 18:40:40 - djelebert assaulted Pennsylvania from California and conquered it from FuegoFuego
2020-06-10 18:40:49 - FuegoFuego received 1 troops for holding Oil AA
2020-06-10 18:40:49 - FuegoFuego received 3 troops for 11 regions
2020-06-10 18:40:55 - djelebert reinforced Dry Dock with 2 troops from Case
2020-06-10 18:40:55 - djelebert ended the turn and got spoils
2020-06-10 18:40:56 - FuegoFuego deployed 4 troops on K3
2020-06-10 18:40:58 - FuegoFuego assaulted Oklahoma from K3 and conquered it from djelebert
2020-06-10 18:41:02 - FuegoFuego assaulted K6 from Oklahoma and conquered it from fairman
2020-06-10 18:41:14 - FuegoFuego reinforced K3 with 2 troops from Oil E
2020-06-10 18:41:14 - FuegoFuego ended the turn and got spoils
Round 10
fairman play first, take 3 regions from FuegoFuego
djelebert play 2nd, and attack the leader, fairman.
FuegoFuego plays, and attack djelebert.
2020-06-10 18:41:14 - Incrementing game to round 10
2020-06-10 23:41:17 - fairman received 4 troops for holding 4 Vals
2020-06-10 23:41:17 - fairman received 3 troops for holding 2 Kates
2020-06-10 23:41:17 - fairman received 3 troops for holding Miners
2020-06-10 23:41:17 - fairman received 4 troops for holding SP Tenders
2020-06-10 23:41:17 - fairman received 1 troops for holding FIS AA
2020-06-10 23:41:17 - fairman received 8 troops for 25 regions
2020-06-10 23:41:22 - fairman played a set of Z7, Pennsylvania, and Dry Dock worth 25 troops
2020-06-10 23:41:24 - fairman deployed 48 troops on San Francisco
2020-06-10 23:41:27 - fairman assaulted Oklahoma from San Francisco and conquered it from FuegoFuego
2020-06-10 23:41:29 - fairman assaulted K3 from Oklahoma and conquered it from FuegoFuego
2020-06-10 23:41:40 - fairman assaulted Oil G from Oil H and conquered it from FuegoFuego
2020-06-10 23:41:49 - fairman ended the turn and got spoils
2020-06-11 00:20:14 - djelebert received 4 troops for holding 4 Zeroes
2020-06-11 00:20:14 - djelebert received 1 troops for holding FIN AA
2020-06-11 00:20:14 - djelebert received 1 troops for holding NY AA
2020-06-11 00:20:14 - djelebert received 9 troops for 29 regions
2020-06-11 00:20:20 - djelebert deployed 15 troops on Dewey
2020-06-11 00:20:21 - djelebert assaulted Phelps from Dewey and conquered it from fairman
2020-06-11 00:20:24 - djelebert assaulted Wasmuth from Phelps and conquered it from fairman
2020-06-11 00:20:29 - djelebert assaulted Montgomery from Wasmuth and conquered it from fairman
2020-06-11 00:20:31 - djelebert assaulted Tangier from Montgomery and conquered it from fairman
2020-06-11 00:20:34 - djelebert ended the turn and got spoils
2020-06-11 10:14:35 - FuegoFuego received 1 troops for holding Oil AA
2020-06-11 10:14:35 - FuegoFuego received 3 troops for 10 regions
2020-06-11 10:14:38 - FuegoFuego played a set of Wasmuth, Z1, and PP Hangars worth 30 troops
2020-06-11 10:15:00 - FuegoFuego deployed 34 troops on Naval Hospital
2020-06-11 10:15:01 - FuegoFuego assaulted Navy Yard from Naval Hospital and conquered it from djelebert
2020-06-11 10:15:10 - FuegoFuego assaulted NY AA from Navy Yard and conquered it from djelebert
2020-06-11 10:15:25 - FuegoFuego assaulted District HQ from Navy Yard and conquered it from djelebert
2020-06-11 10:15:28 - FuegoFuego assaulted Dry Dock from District HQ and conquered it from djelebert
2020-06-11 10:15:32 - FuegoFuego assaulted Officers Club from Dry Dock and conquered it from djelebert
2020-06-11 10:15:51 - FuegoFuego reinforced Dry Dock with 6 troops from Oil C
2020-06-11 10:15:51 - FuegoFuego ended the turn and got spoils
Summary :
Round 7 fairman was attacking djelebert.
Round 7,8, and beginning of round 9, FuegoFuego was the leader and was attacked.
One attack on end of round 9 from djelebert might be deemed unnecessary against FuegoFuego.
Round 10, djelebert attack fairman who is leading.
I see no case in this game.
I took this one as example because FuegoFuego was claming they were teaming in the chat.