From the past year the two that jump out to me are Lupita Nyong'o for Us, and Brad Pitt in Ad Astra. I've actually not seen Once Upon a Time in Hollywood yet, but I refuse to believe Pitt is better in that than in Ad Astra!
Timothée Chalamet for CMBYN.
This year I am really upset that Pain and Glory didn't get a nomination for best picture or for Antonio Banderas' fantastic performance.
It is the best thing I've seen in years. It moved me as much as 1917 in a completely different way.