The phrase "a great killer" is correct and usable in written English.
It can be used in contexts discussing someone or something that is highly effective at causing death or destruction, often in a metaphorical sense.
Example: "The documentary highlighted how the disease was a great killer in the early 20th century, affecting millions worldwide."
Alternatives: "a formidable killer" or "a significant threat."
What everyone is sure of is that the disease has been a great killer.
Although cervical cancer is being beaten in rich countries thanks to Pap smears, it is still a great killer of the world's poor.
A great killer question places an issue deep within your mind, and because you repeatedly return to it over several days or weeks this keeps your subconscious mind active on the subject.
Success is a great killer of innovation: there is an ever greater danger that, as Pixar's list of blockbusters lengthens, its "creatives" will take ever fewer risks and its managers will become ever more complacent (as happened, by the way, at Toyota).
Bastian Schweinsteiger has warned Manchester United's strikers must show a greater "killer instinct" in front of goal or endure another season without silverware.
Completing the three-person cast are Martin Compston as the junior kidnapper and Gemma Arterton ("Quantum of Solace") as a hostage possessed of a greater killer instinct than either of her captors.
Schall demonstrated Ui's transformation from a shabby, impassive gangster into a strutting demagogue with frightening precision, demystifying the "great killer" with a merciless exposure of his mindlessness, shamelessness and criminal fanaticism.
Nuclear war or a virus that makes the leap from animal to man? If, tomorrow, I had to go to Las Vegas and place a bet on the next great killer, I would put all my money on a virus".
How did the father of a disabled daughter end up believing the great killer of the disabled was spiritually guiding him?
A great album, killer singles, nonstop touring: this band from Denton, Texas seemed to do everything right.
"You need an elite goalie, mobile defense, three strong centers and two specialists: a great penalty killer and a dominant scorer in shootouts.
