The Peter Thomas Roth Retinol Serum looks like a nice retinol serum. But have you tried Retinaldehyde? It is stronger than retinol but gentler than Tretinoin. Some good products with this ingredient are the Allies of Skin 1A Retinal + Peptides Overnight Mask, the Medik8 Crystal Retinal, and some Avene products have it too.