Brian from the-digital-picture has done a first look at the Canon RF 50mm 1.2L USM, and compares it against the Canon EF 50mm 1.2L USM and the results speak for themselves. While a larger lens, and expensive, it looks like it's worth the price.
The only caveat to this test is that one camera is the 5DSR and the other is the EOS R, so 1:1 image comparisons will have to take into account the difference of resolution. However, even with that, the results are nothing but a firm statement that the RF 50mm 1.2L is possibly the best 50mm lens that Canon has ever made.
See the comparison here
Pre-Order the Canon RF 50mm 1.2 - Adorama B&H PhotoVideo Amazon