Well the name is POWER liquid 😆 because it is the strongest BHA in Cosrx line. It uses betaine salicylate 4% which is kinda comparable to a 2% salicylic acid but this has Niacinamide in the formula too.
Good thing about this brand, is they recommend you to use it once a week first before going to 2-3 times a week and remembering to use sunscreen during the day.
It is definitely gentle enough to start. Good thing about chemical exfolliants is that your skin will still exfolliants on days you don’t use it.