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