In testing I found that Lash's headshot hitbox is bigger for some characters (Mirage, Viscous, Warden). When in the sandbox I can repeatedly headshot lash while aiming at his upper torso as Mirage. Also his left shoulder sometimes counts as a headshot ~50% of the time. Tested against Paradox to see if this is a property of the larger projectile but her headshot hitbox is not bigger for Mirage.