They all suck. I mean I really wish I could drum up enthusiasm for one of them but I hate all 4 of them in different ways.
Thinker...his arc bogs the show down. He's just not an interesting villain at all. Very bland.
Diaz...the whole thing has been built on the premise that Black Siren is too scared to kill him. She should be the main bad guy. I would probably be fine with him if he was a henchman but I don't buy that this guy can menace a team that's dealt with Deathstroke, Ra's al Ghul and Malcolm Merlyn.
Reign...oh how I hate her most of all. Which is a shame because I liked the actress on House and Banshee. This character is just down right dumb. She has memory lapses and knows it but is in denial that she's a threat to her daughter. She's been told she's an alien like twice now and it never registers. She's been built up as Alex, Lena and Kara's new BFF to the point that it's utterly ridiculous...you know like a Mary Sue where everyone goes on and on about how great a character is and it never seems earned. Oh and you just know this lady's going to die so Alex can swoop in and adopt her daughter Ruby because the whole season's been building to Alex raising the little twerp.
Mallus. Demons now? On the time travel show? Ugh. But at least he's only as bad as everything else on the show. I don't have a major beef with this one but it just seems dumb.
One thing bother me about Black Siren deadly afraid of Diaz she used to work for Zoom speedster who intended destroy other universes