Gears of War 4

The competitive warm-up game mode DOES NOT count towards this achievement even though it is in the competitive playlist. The only current game modes that track for this achievement are:

Escalation
Execution
2v2 Gnashers (Thanks Darth Hawk CZ for the update)

Execution is a faster game mode than Escalation as it only requires killing the enemy team 5 times for the victory, and it does not include wait times for people to place weapons after each round like Escalation.

UPDATE: With the inclusion of 2v2 Gnashers it may be the faster mode despite needing 7 rounds to win if your team is better than the other pairing since the rounds can last as short as 10 seconds. Winning 25 matches in 2v2 Gnashers will also net you the following achievement at the same time so you don't do double the work.

The Don't Hate The Players achievement in Gears of War 4 worth 371 pointsWin 25 matches in 2v2 playlists (public only).

Aside from that the only tip I have is to invite people to play with you as people disconnecting is frequent and if the disconnect is on your team then you’re permanently down a man unless they decide to rejoin the game.

Right ... After putting about 20 hours into competitive to try and get this f**ker of an achievement, I've learnt what works and what doesn't work so, please take notes and let get to work. This is going to be very long winded but please read it all. Don't care about positive and negative votes, so long as this helps people get the achievement. (Edit: Even if you do leave a negative vote, please state why you have and what could be done to improve the solution.)


Boosting
Getting a group of 10 together and trying to match up does work BUT, you will have limited success. Yes, you'll be able to match up and trade wins but, there's a 50/50 chance that you'll match up again or, get matched up against a random team. Over the course of 8 hours (2x 4 hour sessions with myself and 9 other TA members), we matched up enough to trade about 25 wins between the 2 teams. The rest of the time, we were matched up against random teams. By all means, give it a shot, it yielded a decent amount of wins for us, just don't expect to get all 25 wins out of it.

Boosting Update: Motter points out in the comments that be had consistent match up between 2 boosting teams however, the host had 2 Xbox ones and 2 gold accounts. They matched up 12 out of 13 times. Pretty good but, it requires someone to have 2 Xbox ones.


Trying For Legit Wins
Getting legit wins isn't as hard as you may think. If you can get a solid team of 5 together and have great communication amongst you, you CAN win. You just need to know a few things.

Power Weapons: weapons like the Embar, Longshot, Boomshot, Dropshot, Torque Bow and Grenades are crucial to success. On almost every match I played with my team, the opposing team always went for these and no doubt, you and your team will always go for these. Use this to your advantage. Split the team up into 2 groups, one 3 man team and one 2 man team. Rush the main power weapons and possibly the grenades. A mix of Lancer and Gnasher will hold off the enemy team from getting said weapons. Laying down smoke on the opposite side of the power weapons will give one of you a chance to acquire said power weapons giving you a major long range advantage.

Gnasher Is Broken AF: With the insane amount of time and "effort" that The Coalition are putting into competitive weapons tuning, they (unsurprisingly) wrecked the Gnasher and made it so inconsistent, that you'll want to throw your controller through the TV. Some shots will connect and get you One Shot Kills when in close range but, most of the time, they will connect and not a do an ounce of damage. I hit a point blank active reload in an opponents face and did not damage whatsoever as, when he killed me, I didn't see any info about damage I did to him. However, there are some shots that will connect and kill instantly. Luck of the draw so be prepared to rage ALOT! The spread of the pellets is also completely random and this has the biggest effect on damage out put.

Game Type: Pick Execution over Escalation. It's alot quicker to complete. If you know you're going to get steam-rolled by the enemy team, get in there and die as fast as possible and move on to the next match. There will be times where you go on a 4 or 5 match win streak and you'll feel like you're invincible and, there will also be times where you go on a 4 or 5 loss streak and feel like breaking anything near you. Use that angry, get your angry game face on and go kick some ass!!!

Team Play: This is main key to success. Watch each others back, keep your head on a swivel, back each other up in tight gun fights and, above all, MAKE THE DAMN CALL OUTS! One call out can be the difference between winning and losing a round. You see an enemy team member running behind one of your team members, call it out and go back your team mate up. Remember, there is no I in TEAM! Even when you die, you'll be able to see gamertag above enemy team members heads whilst watching your own team members. Call these out too so your team knows where they are.


Summary
This very much boost-able but, don't expect major success with getting matched up. You're better off getting a team of 5 together and just playing matches. Prioritise power weapons, stay together whenever possible and watch each others backs. Call outs are crucial, learn the maps and weapon placements and make that perfect call out that will lead to your team winning the match. Best of luck and go kick some C.O.G and/or Swarm ass!