I'd say that Feathers are the sharpest DE blades, but I can't get a smooth shave with them even in my mildest razors. For me they are as rough as a badgers bum.
Think the Sharpest Blade would be any brand out of Japan, as the Japanese take great pride in product they sell. They IMHO are the most OCD People on earth about what they produce. Be it make P{effect Rice for Sushi, or Sharpes Razor Blade, with most Consistence from blade toBlade. JMHO.
Dealt with Japanese for over 30 years, they are very interesting group of people. Never ever will fully understand them, let just say they make ac big deal out out little nothing in the eye of Westerners.
Japan-made double-edge safety razor blades, single-edge blades for disposable-blade straight razors, and razor cartridges with two, three, or even five blades.