It's Personal: In addition to his obvious feelings towards Steelheart, a number of Epics target him specifically due to his tendency of discovering their weaknesses. Even after Nightwielder's weakness is made (relatively) public, he zeroes in on David for being the one to figure it out.
Nerd Action Hero: He's an excellent shot with a rifle and isn't against killing, but his main boon to the Reckoners is his massive collection of notes and knowledge on various Epics and how to learn about them. Cody outright tells him he needs to get out more.
Obfuscating Stupidity: Less so within the story itself, but growing up he always struggled to hide how intelligent he was, in order to prevent himself from being taken to work for Steelheart.
Red Baron: After the events of Steelheart, he becomes known as Steelslayer.
Science Hero: As much as research on epics can be considered science. It's not his bad analogies or marksmanship that's the biggest advantage to the Reckoners, it's his knowledge of Epics.
One of the Reckoners, a beautiful young woman who helps gather information for the team.
Action Girl: She's one of the team's frontline fighters.
Tsundere: Which confuses David to no end. It eventually turns out that the reason for her seemingly random personality switches is because she doesn't think Steelheart should actually be assassinated. And she's an Epic, so every time she uses her powers she becomes sociopathic.
Prof (AKA Professor Jonathan Phaedrus)
The leader of this cell of the Reckoners, and (as we eventually learn) the founder of the entire Reckoner organization.
The Atoner: One possible interpretation of his activity in the Reckoners.
Ascended Demon: He's an Epic who makes certain not to use his powers on himself so he remains in control of himself. As shown when he does, this is extremely difficult for him to control, but he does anyway.
Badass: When we finally see him fight, it's rather impressive. And terrifying, since he's barely keeping himself from going to be like the other Epics, and the mere prospect of using his powers unrestrained leads him to terrified anger.
My God, What Have I Done?: Almost certainly had one in the past related to being an Epic. And, judging by his hatred of his own powers, he seems to exist in a near-constant state of this.
Mysterious Past: Two variations. In-universe, he's considered an Inexplicably Awesome scientist that worked on Epics. In reality, not much of his past is clear. He was apparently an elementary school science teacher, though this was somehow on accident, and an Epic destroyed the school while it was in session. It's also implied that after he received his powers (It's still not clear how) he had a period of arrogant amorality, but we don't know much about that.
OOC Is Serious Business: When he speaks about his technologies or uses tensors, he is much more harsh and curt with people, as opposed to his normal nice, if determined, manner. This is because he, as an Epic, hates what he is.
Secret Keeper: Is the only one with as much knowledge on the Reckoners as Prof, for plausible deniability purposes on the rest of the team. Furthermore, she is the only Reckoner on the team who knows that Prof is really an Epic.
Superhumans who began manifesting powers following the appearance of the Calamity in the sky, every single Epic is completely sociopathic, with zero empathy for other human beings. The US Government passed the Capitulation Act shortly after they appeared, decreeing that they could do whatever they wished, and that normal humans should not even try to stop them.
Always Chaotic Evil: No matter what your previous personality, use of Epic powers instantly turns you into an evil sociopath.
Combo Platter Powers: The powersets that High Epics get are... interesting, rarely bearing any thematic parallels to each other. Steelheart's invulnerable body and ability to transform non-living matter to steel are thematically parallel, but what about his wind control and energy beams? Or Conflux's electricity powers and his transference ability? Or Prof's disintegration abilities, Healing Factor, and transference power?
Kryptonite Factor: All Epics have a single, seemingly random, weakness that can negate their powers. However they may also have more mundane weaknesses or limitations that can be exploited just as well. For example, an invisibility Epic may be unable to remain invisible whenever they hear a trombone but perhaps they can also be found by someone using a thermal scanner. It's hinted that there's some kind of pattern to this.
Meaningful Rename: Seemingly all Epics take on a new 'superhero/villain' name, one which is usually descriptive or evocative of their powers. Interestingly, the three known Epics that possess some degree of humanity all tend to use their human name, not their Epic one.
With Great Power Comes Great Insanity: All Epics are villainous, but it is unknown whether only evil people gain powers, or if the amount of power they wield just makes being selfish too easy an option. The truth is that using their powers literally, and instantly, changes the way they think. If they are able to resist using their power for a length of time, then their minds will return to normal.
The main villain of the book. Steelheart is a powerful epic who has claimed the position of Emperor of Newcago.
The Cape: Deliberately subverted. His introduction makes it seem like he's a typical example, right down to the lack of a mask and the cape itself, but he almost immediately shows himself to be the exact opposite.
The Dreaded: Makes a deliberate point of terrifying his citizens and potential enemies.
Hoist by His Own Petard: Is a fan of killing people with their own guns. This backfires on him, quite literally, when firing David's gun sets off a detonator within it, ending up killing himself instead due to not being afraid of himself.
I'm Not Afraid of You: He can only be harmed by someone who isn't afraid of him. Unfortunately, thanks to his campaign of terror and propaganda, there is now only one person alive who fits that description.
Kryptonite Factor: The main thrust of the plot is figuring out what it is. He's only vulnerable to people who aren't afraid of him.
Repressive But Efficient: The only reason he's sometimes considered the lesser of the Fractured States' evils. However, this is in a world where 'leaving a complete wasteland where Portland, Oregon used to be' is an adequate comparison for responsible Epics, so make of that what you will. By today's standards, Newcago would be a hellhole.
Intangible Man: Whenever he is seen in public he always has this power engaged, rendering him impervious to harm.
Required Secondary Powers: In order that he not fall into the center of the planet whenever he turns himself intangible, he also has the secondary power of flight. David mentions that this is a common secondary ability for intangible Epics (presumably those that don't have it can be found stuck in the Earth's core).
Tele-Frag: Averted. David was curious as to what would happen were Nightwielder to be made solid while phasing through a solid object, but luckily for Nightwielder he is simply forced out of the object.
My Species Doth Protest Too Much: One of three known Epics with some degree of humanity. Also the first Epic to openly serve humanity instead of trying to rule them, when in Mitosis he takes up the job of Newcago Reserve Power Generator.
Nice Guy: As David notes, the most dangerous thing about him is he might accidentally hit you with one of his hands while he's waving them around as he speaks.
Super Empowering: As a Transferrence Epic, he gives energy generation powers to Enforcement members.
The last of Steelheart's inner circle, an epic with fire based powers who seems to act as Steelheart's bodyguard. David notes that his powers are too simple, and has determined he's actually an illusionist.
Playing with Fire: His fire based powers seem to include turning himself into fire, throwing fire from his hands, manipulating existing fire and generating a projected shield of heat that can melt incoming bullets. Except not; Firefight is actually a powerful illusionist with no fire manipulation powers whatsoever.
Stock Superpowers: Has a classic, if incredibly strong, suite of fire-based powers. Part of what gives away his powers as fake; they're too stock. Every Epic has quirks and oddities, but Firefight is just a fire Epic. Period.
That Man Is Dead: He, like most Epics, sees no worth in his human name. Which, ironically, is why Megan used her real name when infiltrating the Reckoners. Why wouldn't she? It was meaningless to her.
The Mole: His illusionist powers let him spy on and subvert various groups of Epics trying to fight against Steelheart. And the Reckoners.
A fictional Epic created gradually by the Reckoners as part of David's plan to take out Steelheart.
Fake Ultimate Hero: He doesn't actually exist. That isn't to say he's a hero, just that he's trying to depose Steelheart.
Secret Identity: Taken up by Prof as a ruse. Because he actually is an Epic.
An Epic who appears in Newcago after the events of Steelheart in the short story Mitosis.
Achilles' Heel: Like all Epics. His is his own music, which he hated. David theorizes that there's an important clue about a pattern of the weaknesses, but Prof insists that it's completely random, and just a coincidence that this was something obviously connected to him.
A single father raising his son after his wife died. He is noted to be calm, soft-spoken, and a hard worker, who strongly believed that good Epics would come to fight the bad ones. He firmly believed Steelheart was one, to the point of killing Deathpoint in order to save him.