Puyo Puyo Tetris 2

After some trial and error, I have found the quickest way to get this done.

To be sure you get wins, you will want to organise for someone to play with you. You cannot invite a friend to this mode, so you need to both be on and searching at the same time and hope nobody else is!

Choose Online, then Puzzle League, and you will be given the 4 options below:

1. Puzzle League
2. Puyo Puyo League
3. Tetris League
4. Skill Battle League

You want to select Skill Battle League, as you only need to play one round of this mode to win a match.

Make sure to select a team where your primary character is using Tetris pieces.

When the game starts, the player who will be losing the match just needs to press Up (Hard Drop) continuously to reach the top of the screen, at which point the round will end and a win will be awarded to the other player.

After the game, you have the option to search for an opponent again, so just rinse and repeat the above until you have ten wins each.

You will also get this achievement after your first win:

Other guide is great but just wanted to throw this one out there in case someone was wondering if you can do this by yourself with 2 Xboxes (You can!):

If you have two Xboxes with this game, you can boost this easily by yourself. On both accounts: Click Main Menu > Online > Connect Online? Yes > Puzzle League > Skill Battle League

Once here have both accounts Find Opponent. The search should take around 20-30 seconds (there was no one else searching for games as of July 2023). Once paired up, select characters that are Tetris, rather than Puyo Puyo and have the loser press up until they lose. Repeat this process 9 more times and the achievement should pop for the main account.