Here is the full list of all 9 Simp Attack achievements.
Reach wave 10 in the Playground map
Reach wave 10 in the South City map
Reach wave 10 in the Zen map
Reach wave 10 in the Castle map
Reach wave 10 in the Hill Side map
Reach wave 15 while playing Aki
Reach wave 15 while playing Kazuko
Reach wave 15 while playing Kaoru
Reach wave 10 in the North City map