Todd and Lydia (SPOILERS)
With Gus Fring and Associates all blown up at the end of Season Four(and hey, how about that "Two-Face" effect on Gus, eh?) Breaking Bad had to come up with some new villains for the final stretch of Season Five, and they were plentiful: A German-based corporation with roots in fast food AND other enterprises; Prison-gang Neo Nazis "on the outside AND on the inside" and...two very specific specimens:
Todd and Lydia.
Though Todd and Lydia ended up as a bit of a team near the end(based on Todd's unrequited love for Lydia and his attempts to work alongside of her), they moved separately of each other from the most part.
And what was nifty was that both roles were WRITTEN to be very specific in their villainy, and both roles were CAST with actors who seemed to know exactly how to play those roles.
And there was also this: both characters made you wonder about their roots..."what brings people to this kind of evil?" The answers were clearly there for Todd, but never revealed for Lydia.
TODD:
Jesse Plemons is a young character guy with a face that is at once "innocent and ugly." As one critic said of an even uglier actor, Neville Brand, "its like a face that stopped in developing puberty." Plemons has parlayed that face into a career playing "nice guys you just can't trust" -- its just a matter of degree from role to role, and Todd was the worst incarnation.
When Walter White is forced to "switch in" Todd for the more emotional and moral Jesse(Pinkman, not Plemons)...Todd is much more deferential and compliant than Jesse, but...something's off. Trust is an issue.
Todd plays his "psycho" card when he shoots a young boy point blank in the face who witnessed "the great train robbery" -- Jesse punches him, but Walter seeks to work with him. There's something about how nice and rational and apologetic Todd is about this "necessary killing" which allows Walter (and Mike) to accept him.
Walter(now in his ruthless-power-mad phase after killing Gus) sees the value in Todd's connections to that Neo Nazi gang and uses Todd's connections (to "Uncle Jack," yet another new villain for Season Five) to get 10 witnesses killed in three jails at the same time. Walter thus acknowledges Todd's CONNECTION to evil, and uses it. But Walter(and Jesse) still don't see all the way to Todd's OWN evil.
And it only gets worse -- TODD only gets worse -- and by the time Todd has advocated to spare Jesse's life and to hold him prisoner in a cage to cook -- we come to know TODD as a full-blown psychopath whose manner is never less than kind and apologetic. I rather like how while we see all the wounds on Jesse's face and back from beatings and torture that must have been administered by Todd -- we never SEE Todd do these things. Todd is always nice and kindly and helpful in what he SAYS to Jesse. Its what he does(like killing Jesse's semi-girlfriend with a quiet "this isn't personal") that is horrific.
(And indeed, in the follow up Breaking Bad film "El Camino" we see Todd being even MORE evil -- and pleasant, and deferential -- with Jesse in flashbacks.)
LYDIA
Her name's Lydia Rodarte-Quayle, an interesting amalgamation of names. We see that she has a young daughter, and we figure the father is gone. Divorce, possibly. But in this world -- maybe death. His last name must have been Quayle(like the Vice President?)
Upon her first meeting in a coffee shop with Mike, Lydia's great character traits are revealed: She's beautiful(so males in the audience "attach" to her.) She's unscrupulous. And she's SCARED. Nervous like a scared rabbit, eyes often bugging out in fear about what might "get her." Playing against Mike's deadpan professionalism, Lydia is a rather hilarious bumbling amateur -- wanting to meet "back to back" in separate booths (Mike says "OK..I'll come to you.") Calling Mike by a different name to the waitress, who says "Hi, ,Mike"(the working class waitress's mild contempt for Lydia is woman-to-woman: she doesn't like this pretentious idiot anymore than Mike does.)
And yet, for all her flibbergibbet, panicked manner and bumbling ways, Lydia IS smart, and above all, dangerous. The easiest way for Lydia to solve a problem is to have it(or him, or THEM) killed. And in a particularly outraging moment, Lydia asks Todd to guide her, with her eyes closed, through a spread of dead men she has just ordered killed. Lydia literally can't FACE the carnage she orders.
Lydia in "full panic" mode is hilarious. Examples include: (1) Screaming into her office chair pillow when DEA agents are searching her warehouse; (2) Going absolutely apeshit ("No...no...no...NO! Tell me I'm not seeing what I think I'm seeing!"), when grasping a flashlight with the panic and intensity of her personality, she sees a bug on the outside of a chemical canister, and (3) going particularly ballistic to save her life by offering more chemicals for the cook "I...can ...get you...an OCEAN of (it!))