Here is the full list of all 13 My waifu guild achievements.
Present 4 hearts to Petunia
Present 4 hearts to Sonya
Defeat a Level 4 Boss
Present 4 hearts to Liviena
Present 4 hearts to Astarte
Present 4 hearts to Maspalla
Defeat a Level 3 Boss
Present 4 hearts to Silvia
Defeat a Level 2 Boss
Present 4 hearts to Floriel
Present 4 hearts to Camilla
Present 4 hearts to Helga
Defeat a Level 1 Boss