Niacinamide 20% + Zinc 4% Serum

The Amazon-famous Korean lab brand at its most maximalist: double the niacinamide and quadruple the zinc of the usual formula, in a plain watery serum with a plain label. Pore and oil-control devotees swear by it; barrier-first users find the dose gratuitous. Strong opinions per dollar, few rivals.

Around $15