The phrase "weak spot" refers to a vulnerability or area of weakness in someone or something. It means that there is a specific point or aspect that is easier to exploit or attack. Full definition
With my obvious weak spot for this brand, it was impossible to resist trying their fragrance. (thefashionguitar.com)
This expansion exposes weak spots on the surface of the virus that were previously hidden. (sciencedaily.com)
That could be a powerful way to shortcut your research as you begin to draft your reply and find weak spots in your opponent's arguments. (lawsitesblog.com)