There was a study recently discussed on reddit regarding stability of retinol in commercial products. The results are surprising since most expensive serums are most unstable and less expensive serum is more stable. So you can take a look at antioxidants used for that product (there is a table). Looks like Tocopherol Acetate is not enough, they used ascorbic acid + sodium ascorbyl phosphate + EDTA + BHT + tocopheryl acetate.
Surprisingly Granactive retinoid showed the best stability, so if you use it you can take a look at The Ordinary serum and see what formulation they used.