If one were to ask, "What is the most terrifying trait of mindless zombies?" some might say it's their ability to infect. But no, the infection is the virus's doing, not the zombies themselves. Others might suggest their strength or numbers. However, numbers alone can be countered—replace them with any other creature relying solely on numbers, and with enough cruelty and determination, their will to fight can be broken.
What truly makes zombies terrifying is, first and foremost, their mindlessness. This makes them utterly fearless. Then comes their overwhelming numbers, a result of uncontrollable infection. No matter how many of their own are killed, they relentlessly charge through gunfire toward their food sources, undeterred by the carnage around them.
— Ottoman Levant, One Day Later —