The House of the Scorpion
Mr. MacGregor might be even creepier than El Patrón, which is really saying something. This guy is a fellow drug-lord who runs an area near San Diego. Like El Patrón, he's a fan of using clones to prolong his life. Unlike El Patrón, he's got a rather unappealing personality. Check out this description of him in Chapter 10:
He had bristly red hair, a soft, doughy face, and deep circles under his eyes. He looked unwell, but in spite of that, he was in a good mood. He harangued the others in a braying voice and punctuated his statements by poking them in the chest with a finger. (10.47)
Mr. MacGregor is ruthless like El Patrón, but he unsettles Matt in a way that El Patrón never does. Part of this is because he lacks the winning charm that's characteristic of El Patrón. But another part is due to the fact that Mr. MacGregor is Tom's biological father. Matt can't stand Tom, and the fact that MacGregor looks like an older, scarier version of Tom doesn't do much to win him Matt's favor.