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