1. Frank Darbo (Rainn Wilson) is a Textbook Sociopath
Rainn Wilson plays a very Dwight Schrute caricature of a man (deliberate) who crafts a superhero persona to rescue his wife from a drug dealer. While playing the role of the superhero, he displays all of the hallmarks of a sociopath. Deception, no regard for the actual law, physical aggression (he repeatedly beats people in the head with a pipe wrench) reckless disregard for the safety of others (he not only kills and maims people, he gets his only friend in the movie killed) irresponsible in home and work environments, and completely lacking remorse. Darbo is at best an anti-hero that we sympathize with because we've wanted to go smack someone upside the head with a metal object for crimes heinous (molestation) and minor (cutting in line). He is ultimately driven to be with his wife, who in all truth should have never been with him, and left him more than once through the course of the movie.
2. Frank Darbo is Mentally Ill
Frank has a number of hallucinations, and expresses a history of hallucinations, but posits them as the finger of God. This is played straight for laughs and never looked at like mental illness.
3. Liv Tyler is Wasted
In both senses of the word, Liv Tyler is wasted, as Darbo's wife. She is a recovering drug addict, and not so recovering drug addict. She has one lucid scene in the movie, and the rest of the time she is just a prize for Darbo to re-acquire, doing drugs, or almost being raped. This is really an insult to Tyler's acting ability, and an insult to her character Sarah, who is all but the poster for what's wrong with female characters in movies. She has no will of her own, and trades Darbo for her drug dealer (Kevin Bacon), who trades her to another drug dealer who tries to rape her, and Frank takes her back, before she trades him for another guy. She is a masculine fashion accessory and the only glimpse of character we see is Sarah talking to her friend who tells us in a dinner scene that Sarah is a recovering hardcore drug addict and makes bad choices.
Nathan Fillion is an absolute corny delight at Bibleman. Bibleman runs around with two aching conservative midwestern teens fighting Satan (Who I think is played by James Gunn to equally corny shock). Fillion brings a surprising amount of charm and panache to the pedantic Bibleman, complete with cheesy cheesy special effects.
5. Ellen Page is Wasted
Ellen Page's Libby shows up as a by the numbers Manic Pixie Girl working in a comics shop, she helps Frank become his superhero persona, and joins him as his sidekick. She later actually rapes Frank (the only two female characters in the show are tied to rape). Later in the climactic assault on the villain's lair, Boltie gets her skull graphically blown open in front of Frank's eyes. This spurs Frank to go on a killing rampage with guns, knives, and pipe bombs. In the trope of the MPG, Libby metabolizes Frank from the doughty stiff to the Crimson Bolt, she is only thought of one time after, and it is a single comic panel pinned to a wall. Thus, Libby is used as an energizing sexual fantasy, and then is blown away, and neither her act of rape or death have any ramification.
6. Genre Savvy Jacques (Kevin Bacon)
Jacques the Drug Dealer is a delightfully violent and genre savvy antagonist. He carries every scene he is in, and rather than being a card carrying villain, he does some really unexpected things, and his 'evil' is excellent because of this.
7. Zero Consequences
Frank Darbo carries out a prolonged campaign of violence, assaulting criminals and bystanders, culminating in the deaths of something like a dozen people in a bomb throwing bullet storm, complete with corpses all over the place. Darbo faces zero consequences for his actions, suffers no guilt or remorse for the people he killed, or in the case of Libby, people he got killed. Liv Tyler escapes years of drug abuse, being married to a costumed sociopath, a dalliance with a drug dealer who used her as a test mule, to find Mr Perfect, become a drug counselor, and have four wonderful kids.