Here is the full list of all 14 Soulslayer achievements.
Reach a dead end
Save all three from the fire
Complete Lady Xu's route
Complete all the routes
Complete tutorial level
Drink the poisonous soup twice
Poison yourself for all three times
Refuse to do anything until run out of chances
Complete main story and reach good ending
Complete Zhencheng's route
Complete Junyue's route
Complete Yaohongyuan's route
Eye for an eye
Make a successful deduction