This review may contain spoilers. I can handle the truth.
Snake Plissken’s review published on Letterboxd:
This review may contain spoilers.
"Angels and Demons can't cross over onto our plane. So, instead we get what I call half-breeds. The influence peddlers. They can only whisper in our ears. But a single word can give you courage, or turn your favorite pleasure into your worst nightmare. Those with the demon's touch like those part angel, living alongside us. They call it the balance. I call it hypocritical bullshit."
John Constantine (Keanu Reeves) can see things, you know. Demons, angels, stuff like that. Oddly enough, though, people believe he can - mostly because he moonlights as an exorcist, trapping demons - who shall not stay in his plane! - in mirrors and smashing them to teeny bits. World weary and constantly sucking on a coffin nail, Constantine is beleaguered and burned out, a noir detective for the afterlife, if you will. But he's alive; he's just cursed with the gift of seeing demons and angels. And he's a suicide, having been clinically dead for two minutes once upon a time, a time during which he literally saw Hell.
And Keanu Reeves clearly understands Constantine as a noir anti-hero, delivering every line in a world-weary mutter, perfecting a Bogie-esque lip curl, and providing bitter, smart-ass commentary throughout. (Usually this is directed at Angela, but you get the sense that he’d bitch even if there was no one there to hear.)
Angela Dodson (Rachel Weisz) just lost her sister, a patient who jumped off the top of a mental hospital; Angela thinks her sister also Saw Something, and so she goes to John for help. Did Isabel know something? Where is she now? Can Angela see, too? Well, she can, actually, because Isabel was her twin sister, and as we all know twins share everything. So, using Angela, Constantine learns that the Bad Guys (demons), who are supposed to stay in Hell, have been crossing over to the plane of the living, presumably to raise hell. But Constantine knows there's something else afoot, something only witchcraft, voodoo, and other otherworldly things can uncover.
Constantine wanders hither and yon, doing good deeds and helping with crimes involving the occult, and so forth, all with a resigned and rather soulless attitude. Constantine knows he's doomed to a lifetime of doing this, partly because he tried to kill himself and partly because he has The Gift. It's this kind of dispassionate nihilism that plays perfectly Reeves' strengths.
Weisz is pretty good, believable, at least, Gabriel (Tilda Swinton) portrays the angel perfectly as not quite male or female, but the real standout is Satan (Peter Stormare), who was perfect and He added a bit of humor and is Incredibly creepy; he looks like a kindergarten teacher but behaves like a pedophile.
"There's Always A Catch"
The only thing wrong with this movie, is that it completely goes against the comics it was based upon…
John Constantine has never been a Christian in his life, he's a magician.
Constantine is a Terrible Hellblazer Adaption,
But a Damned Good Modern Noir.
Constantine works by using Hellblazer as a jumping-off point, rather than a stone-carved outline to be slavishly followed. In doing so, it creates a moody piece of modern, metaphysical noir.