MultiVersus

My solution, the easiest for us was

Do it with an Boosting Partner or double Xbox in Custom Game Lobby (Local dont work)

We used Superman vs Superman (But I think you can use any Character),I found it easier to use the same Character because it's easier to be in the same Place.

Settings
2 Person Version
Game Mode: 1 vs 1
Time: 2-3Minutes more u dont need should be more than enough
Knockouts: 4
MAP: Trophys E.D.G.E.

THX to dubdeetwothree his idea
Settings
4 Person Version (100kills possible for the booster persons in 15mins)
Game Mode: Free 4 All
Time: 15Minutes
MAP: Trophys E.D.G.E.
(for the 4 person version, switch roles after the round and play another round so that everyone gets the achievement)

Once the round starts, go to the right or left edge as far as you can (one step too far and you'll fall off) there's some space, but not much.
Your boosting Partner or the double Box goes to the same place.
Do a double jump with , and then press + to hit the Partner ( the double Box) from the edge
Now run the Boosting Partner or double Xbox back to the same place and repeat the step from before
Do the Rematch and repeat

I made a Video to make it more clear


ps:if you have your Routine in place, 8 points Match + Rematch should be easy
Sometimes it doesn't work because you're not close enough to the edge so i chose the same Character as the other side and that made it pretty easy for me to finish it