SUPER BOMBERMAN R

This solution is for double-boxing.
Edit: This also works for boosting online with 1 or more friends. Just multiply the time and games played by that extra amount of people.

1.
From the start menu, go to 'Battle' then 'Online Battle'
In the Online Battle screen, select 'Free Battle' followed by 'Create Room'

2.
Set the 'Room Type' to 'Friend Room', change the amount of 'Sets" to 1
Confirm these settings with A
Pick whichever stage you'd prefer.

3.
Now on Xbox #2, make sure you have another account.
Edit: Have your boosting partner(s) do these steps.
Go in to the 'Online Battle' menu.
From there go to 'Find Friends', it should pop up showing your room.
Join the room and select whichever Bomberman/Accessory you prefer.

4.
Once in the match, self destruct with Xbox #2.
Edit: Have your boosting partner(s) self-destruct.
When the results screen shows up, select 'Exit' from the menu on both (Edit) /all consoles, which will take you back to the 'Online Battle' menu.

For Boosting parties; Have the next person in your rotation 'Create Room'

Repeat from 2.

Comment if somehow this isn't precise enough.

This solution is the fastest method I've found and it works!

find a partner and add it to your friends list

Battle
battle online
free battle
creates room
set 1 round and all other settings leave them like this
Map is indifferent, all are fine

you will ask "so? what's strange about this method?"
With my friend we did 1 game each alternating, but it didn't rise the tracking of the achievement, we tried several times and nothing... we changed skins and map, it doesn't work ... then I got an idea I tried to do 5 games in a row to be host to see if it worked, and that's it! practically the tracking doesn't go up if you alternate the host with other players, so the secret to make it go up is to do everything in a row obviously then you'll have to do the same thing for your friend.

If you decide to interrupt your host game remember that then to make it go up you will have to make a blank game, if you interrupt and give your friend the possibility of making host, as soon as you are the host the first game will never work, the counter will rise from second and then all in a row will go up by +1, the same goes for your friend, after your 100 games, your friend will be host but his first game will not go up the counter, from the second one. I don't know why this happens, most likely it is the counter glitch but with this method I had no problems.

Tip: to make everything less painful instead of sending each game invitations (or receive them when you help) add your friend in the friends list create the room and automatically tell him to go to find friends every time, there will be only 2-3 seconds of upload and you won't waste time with loading screens and invitations, THE SUICIDE METHOD WORKS!!! commit suicide as soon as the game begins you or your friend, it will end in 2 second (it doesn't matter if you win or lose, you just have to play).

This is my first guide, don't be bad.

Set-up an online multiplayer game by going to 'Online Battle' then 'Free Battle' followed by 'Create Room' with these settings:

Rules: Battle Royale
Player: 4P
Room Type: Open
Sets: 1
Time: 9
Start Position: Fixed
Revenge Carts: On
Pressure Blocks: On
Skulls: On
Special Abilities: On

Pick 'Pitfall Zone' & any Bomber Type and wait for a second player to join your room.

When the game starts press B to drop a bomb to end the match and proceed to the Tally page at which point you should press 'Exit' to make the match count towards 'Room Master' & 'Room Champ'.

Now you must repeat the process and create a new room each time. If you have a friend that can assist, you can change the Room type from 'Open' to 'Friend' and invite them this way.