To see the -Complete- banner on your save file, you need the following. Print this checklist:
9/10 – A refreshing "scramble" on the tired DLC model. Just don't blink, or Kenji will steal your swimsuit DLC right out of the tide pool. -ENG- Summer Vacation- Scramble All DLC -Comp...
-ENG- Summer Vacation: Persona 5 Strikers – The Ultimate All-DLC Scramble To see the -Complete- banner on your save