Nine
Enneaphobia (from Greek ennea meaning "nine"), also known as nonaphobia (from Latin novem meaning "nine"), is the fear of number nine. It is mainly feared in Japan as nine in Japanese is similar in pronunciation to their word which translates to suffering.
There's also a superstition connected with the history of classical music. This belief is believed that a ninth symphony is destined to be a composer's last, and that the composer will be fated to die while composing it, after composing it, or before completing a tenth.
Enneaphobia may commonly be triggered due to being disappointed of achieving near=perfect scores or near-completions, like achieving 9/10 in the quiz often but rarely getting 10/10, while seeing a family member die less than a year before their new decade (e.g. dying at the age of 69).
Enneaphobia is usually not a severe phobia, but sufferers would often avoid the triggers. Enneaphobes would try to avoid encountering numbers with the digit nine (19, 29, 39, 49, etc.).