Fuzion Frenzy 2

If you get 4 players, you can do over the falls. If no one presses any buttons you all fall off at the sametime and get first place. Do that 10 times and all 4 will get the achievement. Works for custom game too.

If you have 4 people, definitely do Over the Falls and everyone will get the wins at the same time.

If you don't have 4, play Aqua Blast. Kill the AI, then have the remaining players stand on the same platform (preferably an edge). When that platform goes, everyone will die at the same time and everyone gets the win.

This way there's no reason to take turns, and you can finish in exactly 10 plays... which is plenty already.

To append to OtisFamily's comment, AquaBlast is probably the fastest game you can play to get this achievement. Just double team the CPU players take turns diving off the edge.

We managed to get a pretty good system down where the actual game play for each round took about 4 seconds.

1. From the Main Menu, select 'Online Battle', then choose 'Mini-game Frenzy'.

2. Create match, 'Open' as the session type.

3. Change players 3 and 4 to 'COM-Easy' by pressing X and making the selection by pressing A.

4. Invite a friend/boosting partner to the room.

5. Press RB to choose the 'Aqua Blast' mini game and start.

6. Alternate wins between 1P and 2P, and use 'Return to Lobby' each time to setup the next match as step 1. Players in the sessions already, will remain there. Doing things this way, will ensure accurate win counts.

7. Repeat for a total of 20 matches (10 wins each), and you and your friend will net the 'Mini-game Frenzy Hero' achievement.

Congrats! :D