Question: who is the main killer in pretty little liars?
Answer: Alison Dilaurentis killed Ian Thomas when he was trying to kill Spencer. Mona Vanderwaal killed Bethany Young and Melissa Hastings buried her alive, Bethany Young killed Marion Cavanaugh, Toby Cavanaugh's mom Detective Wilden killed Garret Reynolds, Hanna Marin killed Elliott Rollins (real name: Archer Dunhill).