Ahoy Matees! Welcome to Sea of Thieves!
The below video discusses the best place and fastest way to get this achievement after the shrouded spoils update!
Artie has supplied a text guide of where you can find Villainous Skulls so I will not replicate that here (drop him a like), but the below video is a guide that I think is the Fastest way to get Villainous skulls as well as get the achievement for killing 1000 captains (Hunter of the cursed captains achievement says 700 but still needs 1000 as of right now), and obtainining 150,000 gold in the Order of the souls (Mercenary of the Order achievement).
I hope you find the video helpful!