Starting with MePhone 4S, the MePhone starts to look more and more threatening every generation. They state that their mission is to kill their predecessors, but there is one episode where their creator states that they're just there as product placement.
While Ghost Bow generally acts friendly, she is introduced in a way that scares the contestants. Her edges are still ripped up from going insane in the season 1 finale.
Mephone 3GS sounds terrified whiling glitching out in one scene in II season. This might be a bit terrifying for younger children.
In my opinion, Season 2 is the most intense and terrifying season of the 3 so far.