Here is the full list of all 29 Scarlet Maiden achievements.
Completer the quest ‘It’s a Strap’
Complete the quest ‘Green Delight’
Defeat Queen Lily
Complete the quest ‘Magic Flute’
Level Faelina to level 5
Defeat the Grand Archivist
Level Bruce to level 5
Level up to level 50
Gain 100000 sin total
Level Roman to level 5
Slay 100 enemies in one run
Find 50 items in one run
Complete the quest ‘Masquerade’
Earned after 10th run
Gain 15000 sin in one run
Defeat the Earth Mother
Find 20 items in one run
Level up to level 10
Complete the quest ‘Steamy Contraptions’
Slay 200 enemies in one run