There is no upper limit on the maximum effect that can be detected in randomized trials. https://www.jclinepi.com/article/S0895-4356(25)00161-1/fulltext
Article reporting research that used five cohorts of randomised trials of cancer treatments (716 trials comparing 984 experimental versus standard treatments in nearly 350,000 patients, conducted between 1955 and 2018) to predict the maximum discoverable treatment effects in cancer trials over the next 50 years.
