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