Modern fiction seems to shy away from the true, unapologetic omniscient voice you find in the classics. A lot of what gets called omniscient today is just a close third that occasionally head-hops between two main characters. For a real, functioning example, I keep coming back to 'A Little Life'. Hanya Yanagihara uses that narrator like a hovering, grieving angel.
It knows everything about Jude's past, the secrets he keeps from his friends, and the internal wounds of the other characters. The narrator isn't just reporting thoughts; it's framing the entire tragedy with a kind of brutal, predetermined sorrow. The voice has a distinct personality—it feels compassionate yet relentless, like it's showing you this beautiful, horrible tapestry and you have no choice but to see every thread. That's the power a real omniscient narrator holds: it controls the emotional weather of the entire novel, not just the internal climate of one person.
It creates this devastating irony because we, the readers, understand the full scale of the tragedy long before the characters in the story ever can. That gap between what we know and what they know is the entire engine of the book's emotional force.