Narrowing this down to 20 is really challenging. And like Jeff, I can rattle off at least a dozen characters per show. I think 5 per show is probably where I have to keep this.
Some things that I won't be listing? Male Imperial officers. With the new Admiral Piett and Moff Jerjerrod on the way, it seems that we're probably going to get a number of Imperial officer figures using that new buck. So while I think they would be great to include in my list, I'm going to skip Colonel Yularen, Major Partagaz, Captain Tigo, Valin Hess or Titus Welliver's Imperial cruiser captain in The Mandalorian.
THE MANDALORIAN
Greef Karga (season 1)
Cobb Vanth
Covert Mandalorian - Nevarro street battle
Migs Mayfeld (season 1)
Captain Carson Teva
THE BOOK OF BOBA FETT
Boba Fett - Tusken captive / Toschi station
Pyke Enforcer
8-D8
Mayor Mok Shaiz
Tusken Chieftain
OBI-WAN KENOBI
Grand Inquisitor
Princess Leia
Owen Lars
5th Brother Inquisitor
Tala Durith (The Path)
ANDOR
Luthen Rael (Ferrix)
Dedra Meero
Temaryn Barcona (Aldanhi heist)
Brasso (Funeral)
Imperial Riot Trooper (Ferrix)