Let me start by saying just how terribly slow and dead the matchmaking is for this game! As such there are three ways to get this achievement!Method 1:
Go to "online vs Players" search for your chosen game type and hope that someone is also searching at the same time (Highly unlikely!), play the game to completion be it a win or lose. Rinse and repeat these matches 24 more times and the achievement should be yours!
Have a friend who also has the game and set your search paramaters the same (1v1 only ticked & public) and then search, to which you should eventually be matched together. Either play the game or have one person quit the match! 25 times in total and achievement should be yours...P.S, If you're quitting/surrendering a match i don't believe that player gets credit for playing the match, so it would be a case of trading off "wins" until you have the amount. This is from my own experience using my solo method.
My personal favourite is the solo method as it doesnt rely on anyone else. Using a similar method as detailed in the "Comp-Stomp Officer" achievement guide i wrote;"Setup a second xbox account/email and go on to create a second profile on your PC with these details (Or if you have it available use a second laptop/pc that can run the game, if you don't there will be a lot of account switching).
On the second account, sign up to xbox games pass PC for a measly £1 trial month! Attempt to install the game on this account and it should instantly install (If on the same PC). Fire up the game on gamertag #2"
Now, switch between accounts as neccesary and put both of your accounts into the "Automatch vs Players" menu. Set both accounts to public
and only to search for 1v1
game modes. When ready, start your search with one gamertag before switching accounts and starting the search with the other.
Your accounts should evntually find each other and start a match. Under your second account when the game launches, simply surrender the game. This doesn't give that gamertag any credit towards the achievement but your main profile will be given a step closer to that 25 matches progress.
Simply quit to the menu and repeat the search process your required amount!