A Quick Easy way to get the achievement:
Load up your game and go into Quick Battle in Offline Mode. You character selection doesn't really matter, there are several you could pick for this. You only need a character that has an uppercut sort of move. For me, I chose Siegfried, if you hold Diagonal Down Right and tap Y repeatedly between hits, he will perform quick uppercut hits.
Select your search criteria to Easy difficulty and look for a character named something along the lines of "Negink6080", an Ezio character with the title "Assassin Trainee". The map in this fight is surrounded completely by walls. All you have to do is push your low level character into the wall and repeat uppercut hits. If you don't get it in one game, rematch. You should get 4/5 maybe 6 wall hits from each game if you get a good routine going.
Hope this helps :)