Andy Nelson’s review published on Letterboxd:
It's difficult to make films designed to laugh at such painful parts of history as Nazism and Hitler's rule. Taika Waititi, a native New Zealander with Maori heritage, may seem like a strange person to take on the job, but here he is, not only making a comedy about a young boy growing up with dreams of being a great Nazi, but also playing the role of the Führer himself. What Waititi does is create a world that allows us to laugh at the fanaticism of Nazism, even during the period depicted in the film here when it's on its last legs as the war is coming to an end. He allows us to laugh at the absurdity of it all, and how everything's okay as long as they still have something to hate that's worse. Jews were the worst, but when Russians invade, Jews don't seem so bad when compared to the invading forces. A gay captain? As long as he's teaching the kids how to throw grenades, no one bats an eye. It's smart storytelling and smart comedy.
Of course, the real story here is Jojo who is so devoted to Hitler that his imaginary friend is Adolph himself, wonderfully played in all the best over-the-top ways by Waititi. Jojo discovers a young Jewish girl living in his walls, hidden there by his own mother (the traitor!). Through this discovery, as well as his own mother's actions (wonderfully played by Scarlett Johansson), Jojo finds himself challenged as to his beliefs about what's right, and it doesn't help that little Adolph sitting on his shoulder has plenty to say about things. The acting is sharp and balances perfectly between comedy and drama, and the story gives us the moments we need to have the weight Jojo needs in making his decisions.
It's a wonderfully crafted story that makes you laugh one minute then breaks your heart the next. In the end, it's not quite as effective as I wanted it to be, but it's still a beautiful and powerful way to depict struggles in Germany at the end of WWII.