Please recommend high-concentration Vitamin C cosmetics with fast whitening effects.

I usually use Vitamin C, niacin, and retinol for whitening care.

I mainly bought and used Vitamin C derivatives or hypoallergenic products.

However, since I bought these products when my skin was very sensitive, they are on the milder side.

Since it is quite mild, even though I have used it for a long time, my skin texture has improved, but the whitening effect seems minimal.

My skin is currently in good condition and doesn't get irritated no matter what cosmetics I use, so I'm planning to upgrade to the next level.

I plan to provide more active and intensive management to see results.

I've been keeping an eye on IOPE products on Unnie Deal. Please share your reviews if you use them.

Please recommend high-concentration Vitamin C serums, ampoules, and essences.