I recently demoed the Sigma DG DN Art 50mm f/1.2 for the L mount and am really impressed! The sharpness and falloff at f/1.2 is incredible.
I thought the Canon RF 50mm f/1.2 was the best, but the Sigma has to be one of the best lenses I’ve used in the 50mm FL. The build quality is outstanding and much preferred over the RF. Even the packaging, warranty, shoulder carry lens bag is very Leica-like at a substantial savings. Japanese quality and price make the Sigma’s a nice, competitive option for the L mount.