Eurus Holmes (Sherlock)

Eurus Holmes is Sherlock Holmes' sister and the main antagonist of season 4 of Sherlock. She is also a Villain Sue who's intelligence is basically a magical superpower.

Why She Sucks

 * 1) She feels more like a Saw villain than a Sherlock one.
 * 2) She's a Villain Sue who's IQ somehow gives her mind control powers that convinced the people running the asylum she's in to let her come and go and remove the glass panel from her cell. She's also somehow able to take over the place all by herself.
 * 3) * Sherlock also somehow doesn't notice the glass panel is gone.
 * 4) * She's also somehow able to predict terrorist attacks in an hour's time based on Twitter patterns.
 * 5) * She's somehow able to convince Mycroft Holmes to allow her, a psychopath obsessed with Sherlock Holmes, to talk with Moriarty, another psychopath obsessed with Holmes for five minutes unsupervised. This requires a huge IQ drop from everyone. Also, Eurus is somehow able to formulate a plan at least two years in advance within five minutes. This is ignoring all the variables even a genius would not be able to predict. What if Mycroft lied about them being unsupervised? What if he brought backup or had Eurus moved to another facility? What if nobody decided to play her mind games? It also raises the question of why Moriarty would help her with a plan that ends with her and Sherlock reconciling with each other.
 * 6) She also retroactively reduces Moriarty to a pawn. This is especially bad given that Moriarty was teased at the end of season 3 only for it to turn out he really is dead.
 * 7) Her freudian excuse basically amounts to "she was better than everyone else" and just "wanted Sherlock to love her". It also falls flat given that she murdered Sherlock's best friend, acted like a psychopath through the episode, played deadly games with Sherlock, Mycroft and Watson, killed a nurse (and possibly raped her) and hostages and forced a guy to kill his family.
 * 8) Her "redemption" is just saving John Watson who was only in danger because of her.
 * 9) Sherlock just forgives her for everything she's done, making her a downplayed Karma Houdini.