I've been thinking about this question. Which actor, who currently doesn't have a competitive Oscar, is most due? This is limited to actors who are alive and not retired, so I'm excluding Clint Eastwood and Robert Redford, although they can count as "other" if you think I'm wrong about them being basically retired from acting.
Some may have honorary Academy Awards, which are hard to get, but that's not relevant to this question.
I'm limited to 14 choices and other....
Amy Adams- She's been nominated six times, and should've been nominated for Arrival.
Angela Bassett- She was considered due when she became the first and only actress nominated for an MCU film. She's also nominated for playing Tina Turner in What's Love Got to Do With It? and her other credits include Malcolm X, Boyz N The Hood, How Stella Got Her Groove Back, Passion Fish and the Mission Impossible series.
Glenn Close- She was the frontrunner for The Wife and considered due before Olivia Colman won. She got another nomination since then.
Toni Colette- It takes range to play her characters in The Sixth Sense, Little Miss Sunshine, Hereditary and Knives Out.
Tom Cruise- Possibly the last remaining true movie star.
Matt Damon- Well-deserved nominations for Good Will Hunting, Invictus and The Martian. Likely in the running for Oppenheimer.
Willem Defoe- He established Norman Osborn as the archenemy for two Spider-Men, in addition to Das Boot and Oscar-nominated performances in Platoon, Shadow of the Vampire, The Florida Project and At Eternity's Gate. He has range and works really well in specific situations.
Robert Downey Jr- Seems to be gunning for a supporting Oscar in Oppenheimer. Possibly the definitive action hero of the 21st Century as Iron Man. Oscar-nominated for Chaplin and Tropic Thunder.
Ralph Fiennes- He's been in three best picture winners with Schindler's List, The English Patient and the Hurt Locker. Voldemort's other major performances include Quiz Show, The Constant Gardener, In Bruges and last year's The Menu.
Harrison Ford- Potentially a bigger movie star than Tom Cruise.
Samuel L Jackson- He's getting some press complaining about how he wasn't nominated for Jungle Fever and how his best scene was cut from A Time to Kill. His sole nomination was as the best-regarded performance in Pulp Fiction, which some view as the best film of the 90s.
Tony Leung- The only man on this list to never be nominated for an Academy Award. In the Mood for Love may be the best regarded movie of the 21st Century (Sight & Sound certainly thinks so) and other major performances include Chungking Express (which Sight & Sound rated above the American trinity of Pulp Fiction, The Shawshank Redemption and Forrest Gump), Happy Together, Infernal Affairs (the basis for The Departed), Ang Lee's Lust, Caution and Hero.
Ian McKellan- The frontrunner as Gandalf. Other performances include Magneto, a former Nazi in Apt Pupil, a tortured director in Gods and Monsters and various theatrical adaptations.
Naomi Watts- Mulholland Drive is very well-regarded. She has also been nominated for 21 Grams and The Impossible, in addition to acclaimed performances in The Painted Veil and Best Picture winner-Birdman.
I do not have room in the pool for Bradley Cooper, Johnny Depp, Charlotte Rampling or Isabelle Hubert. And that is among working actors. I'm sure there are others I left out, so there is the "Other (Please Specify)" option.