the broadchurch slug is one of the more obvious visual metaphors for finally catching and “stomping out” danny’s murderer, an intruder to their home. imo it’s even more effective as an illustration of how ellie’s feelings change between this first scene (left column) and second (right column). the muted, matter-of-fact way she kills the slug reflects how removing the “monster/invader” from play hasn’t healed the damage he’s caused - there’s no catharsis here, but a disillusionment and disgust causing her to kill what is ultimately a pretty pathetic threat.
also, that slug sure lingered about didn’t he. R.I.P.