Walt's terrifyingly dumb up until the last few seasons, then he actually started to get more scary, especially in Felina. Gus can be on and off with his amounts of terror, making him actually terrifying most of the time, much like Todd. Tuco was literally insane. Fucker had a goddamn M14 and was in a different DIMENSION from all that Blue stuff he definitely snorted before kidnapping Walt and Jesse. Todd didn't really get to do that much, but he was kind of scary. He was that "Nice on the outside, Nasty on the inside" type of terror, unlike his uncle Jack. but Jack was just an asshole so he doesn't really fit in here. The Cousins were Mexican Agent 47's, which makes them terrifying enough. And I haven't watched BCS yet, so I have no fuckin clue who the last guy is. All I can say is that he looks like Trevor from GTA, so I assume he's about as insane, if not, half as insane as Tuco