To answer the OP's question: yes, all it can take is one complaint. Especially if the complainer has made many complaints to
ebay and has built up a reputation of usually being right. You can bet if someone like swamperbob or SsuperDdave files a complaint about a coin in their area of expertise,
ebay is much more likely to listen and act quickly than if a random eBayer does the same.
That doesn't, of course, mean that
ebay will always ignore complaints from random eBayers. They sometimes act on them; it all depends on the human which the report eventually makes its way to.
ebay's complaints handling is so understaffed their responses to complaints can probably be best described as "inconsistent". Many people on this forum can probably share stories about how blatantly bogus or fraudulent listings they have reported were allowed to remain, while some of their own listings have been pulled for an accidental and relatively minor infraction of the Rules.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis