The sheer joy and charisma brought to this role by Gary Oldman are the only substantive reasons to see Darkest Hour. Beyond his performance, there is only a slow-burning and largely failed attempt at drama. Stream this one.
The Good: Gary Oldman and his makeup.
The only true and substantive reason to see this movie is Gary Oldman. He has a mixed track record as far as movies go; Robocop  was not great.
But it can’t be said that he doesn’t try his best. He’s a very animated and verbose actor. Oldman seems to pour his soul into every single part, no matter how silly or grand. Here, he gets to put those tendencies to use, coming alive as Churchill.
Oldman is boisterous, blubbering, timid, playful, coy, boiling, and stately, all with the same level of ease. It is a role tailor made for him.
The role is as physical as it is emotional of course, and without some excellent makeup, it would not have been accomplished. Nominated for that work (among others) is Kazuhiro Tsuji, known for his work on The Curious Case of Benjamin Button, Hellboy, and How the Grinch Stole Christmas. This is certainly among his best work; save for holographic recreation, it is unlikely that a more realistic Churchill could have graced the screen.
The Bad: The point of the film is clear, but the drama is still mostly flat.
Unfortunately, this is not one of those cases where a single performance saves an entire film. While Darkest Hour is by no means a bad movie, it is inescapably boring.
To understand why, one has to look no further than its antithetical contemporary, Dunkirk.
Both movies are about the same event, essentially. Darkest Hour is the prequel, and Dunkirk is the main event. For everyone but the most ignorant of history, the outcomes of both films are already known when walking in. Yes, the British continued to fight WWII against the Nazis, and yes, they managed to get their armies off the French beaches. The difference lies with where the resolution lies with each film.
Dunkirk recognizes the predetermined outcome of its story. Instead of asking the audience to cheer for this known-ending, the movie instead asks that you invest emotionally in its characters. We know the British are successful in pulling their men off the beach. But that doesn’t mean that Tom Hardy, Cillian Murphy, Mark Rylance, or Harry Styles will survive. Their fate supersedes that of the larger picture. It is dramatic, and successful.
In contrast, Darkest Hour is only about the larger picture. The primary question the film poses is, “will Churchill succeed in persuading the British to stay in the war?” Except that question is already answered. Yes, obviously.
The drama is kneecapped by its outcome. This is not always a death sentence; we also know how Lincoln was going to end. Successful stories with this issue invest in the characters rather than the outcome, or they provide a compelling enough journey. Darkest Hour provides neither.
The emotional elements of the story are forgotten almost immediately. Is Churchill forced to be a nicer person due to the arc started with Lilly James’ character? Not really. Does his inevitable victory in convincing British parliament to stand up against the Nazis destroy or strengthen his personal relationships with his wife and children? Who knows. They are forgotten during the second act.
The Ugly: It’s well past time to stop lionizing Churchill.
Ironically, Darkest Hour isn’t really about the historical event it is portraying. The story itself is obvious, and gratifying; in the face of dictatorial tyranny, there can be no quarter, no deals, no terms. Capitulation in the face of demagoguery means doom. It is timely, to say the least.
And yet, the same story could have been told without lionizing Churchill. He is one of the few foreign figures that has gained legendary status in American lore. Every single child learns about him, however briefly, in school. The third member of the great triumvirate of the Allies, standing up against Nazi Germany.
We never learn about his horribly racist views on Indians, or the famine in Bengal, which killed millions, that he had a direct hand in causing. We never learn about his orders to fire upon hundreds of Greek protestors, or his advocating of bombing into submission rural tribes in Iraq, or the concentration camps in Kenya, or his hatred of the Irish.
None of this detracts from his part in convincing the British to stand up to Hitler, when the alternative may have had disastrous consequences. But it does mean that Churchill should not be celebrated. The horrors that he inflicted, directly and indirectly, on millions of others deserve more than a few throwaway lines of dialogue from the antagonists of the film.
“During the early days of World War II, with the fall of France imminent, Britain faces its darkest hour as the threat of invasion looms. As the seemingly unstoppable Nazi forces advance, and with the Allied army cornered on the beaches of Dunkirk, the fate of Western Europe hangs on the leadership of the newly-appointed British Prime Minister Winston Churchill (Academy Award nominee Gary Oldman). While maneuvering his political rivals, he must confront the ultimate choice: negotiate with Hitler and save the British people at a terrible cost or rally the nation and fight on against incredible odds. Directed by Joe Wright, DARKEST HOUR is the dramatic and inspiring story of four weeks in 1940 during which Churchill’s courage to lead changed the course of world history.” – Rotten Tomatoes