My suspicion was right, 50/1.8 L-mount lens is one of the best 50mms.
And 50/1.2 is not a slouch neither, though 50/1.4 is a bit sharper.
Thanks to Nester @MFlenses.com for this information/data.

I used 50mmF/1.2 for 5 years from 21 to 25 (1965 to 1969), just borrowing
my brother-in-raw's Canon 7 together to shoot their twin boys and more
using Kodak Tri-X pan exclusively since 100 feet film was relatively cheap.