One of the simplest examples of biological unfairness is grip strength. Studies like the one below show that 90% of females produced less force than 95% of males. (In english, if you're the weaker than 19 out of 20 men, you're still stronger than 9 out of 10 women). It gets worse, female athletes and their maximum force is 444 N, that's still below the average for men (541 N), and is in fact below 3/4ths of all men (most being non-athletes), and all male athletes. In sports where grip strength maters, trans women (M2F) are going to always have an unfair advantage that can never be compensated for.