Larxene Data is definitely one of the hardest Data Battles at Level 1. I would've skipped her Desperation Move, but the game makes you stop looping her at about 5ish bars of HP because If you don't stop looping her you will die even if you Quick Run. I was able to manipulate her AI in the third phase by jumping and using Horizontal Slash to make Larxene go into her Desperation Move. This is pretty much the Dean Challenge, but just using the Sweet Memories.
Restrictions: Level 1 No Damage No Hit No Armor No Accessories No Drives No Magic No Limits No Summons No Stat Boosters except for Roxas' AP+ 2 Must use the Sweet Memories