You do not need 10 different replays for this. You don't even need to watch the replay all the way through.
Replays are saved after doing a verses match or an online match.
Just go into verses mode (you need two controllers, it won't save a replay vs the computer) and win a match. I had it set to one round and I just did the instant kill. After the match it will ask if you want to save the replay, say yes.
Go to the database menu and load up the replay.
Once the replay gets to the start of the match you can quit back to the replay menu.
Just do that 9 more times. The trophy unlocks while loading the 10th replay.