I want to say Bendix. I also want to hear the position of Luthor supporters.
What are Henry's best prep/tech feats? I hear he's really dangerous.
This is by no means comprehensive, I'm just going off what's coming to mind as I write. He made Midnighter and Apollo (and the rest of his own personal JLA), he has a catalog of every non-magical superhuman ability he has come across and developed a process to incorporate them all into his body, an abandoned base of his that was found after his death was run by a virtual copy of himself and had systems set up to cause world-ending disasters across the planet (just to stall the reality-warpers on The Authority), he's invented a device that creates limitless energy, he has robot armies, he has cloned versions of all the superhumans he has made, he's enslaved the Spirit of Murder, he has his own Carrier, he travels through time and dimensions, he has goons with shape shifting abilities so good that they could trick Midnighter into thinking one of them was Apollo (because they can actually just become, right down to the DNA, whatever they need to), he discovered The Bleed and even as a child he was messing with aliens from other dimensions. His specialization (if he has just one) is the integration of technology and organics, which results in tech seamlessly integrated into his mind and body, power implantation, and building superhumans.
@Needlebay: I wouldn't say he's smarter than Tao. He's certainly displayed far greater technological ability than Tao, but I don't know if he's necessarily better. Tao's way more interested in screwing with people (on a small or large scale) than building things. His few technical feats have been been decent though, a virtual reality prison for his enemies and the knowledge he displayed of interdimensional alien tech in Coup de Tat.