0.1% is the highest % of Retin-A that I am aware of.
It takes months for results to maximize. It will not help with crows-feet or other deep lines. It does help with clarity, smoothness and lessening of fine lines.
Read THIS about Retin-A and other retinoids/retinols. If you really have resistant skin you may need to up it to tazarotene, the strongest formulation of retinoid.