Fortunately, in Catholicism, the 20th Century began with Pope Leo XII, then Pope St. Pius X, and also Pope Pius XI, Pope Pius XII, Pope John Paul I, Pope John Paul II (to be known as The Great), and Pope Benedict XVI, and several lesser lights. Also Cardinals Merry del Valle, Amleto Cicognani, Carlo Confalonieri, Alfredo Ottaviani, James McIntyre.
In the United States, we had Presidents William McKinley, Theodore Roosevelt, Warren Gamaliel Harding, Calvin Coolidge and Ronald Reagan and the dark side consisting of such as Woodrow Wilson, Herbert Hoover (as president but he improved in private life), Franklin of the New Deal (although concededly also Dr. Win the War), Harry Truman, Dwight Eisenhower, JFK, LBJ, RMN, Gerald Ford, Jimmuh Peanut, Bush the Elder (and Tax Hiker) and the Arkansas Antichrist.
In popular culture: 1950s DooWop, the Beach Boys, the Big Band Era, the Blues, Frank Sinatra, Nat King Cole, Bing Crosby, Elvis, Buddy Holly, Motown, Natalie Wood, Clark Gable, Vivien Leigh, Gone With the Wind, Dr. Zhivago (even though the author was a Gramscian communist), Godfather I-III, Seven Samurai, Sound of Music, American Graffiti, popular novels by writers like Clavell, Clancy, Baldacci, Grisham, Deaver, Jeffrey and Kenneth Shaara, and by Taylor Caldwell, histories by Samuel Eliot Morison and Allan Nevins and Paul Johnson and Crane Brinton and Donald Kagan and Shelby Foote, and biographies by Robert Caro and by James I. Robertson and by George Weigel and American Caesar by William Manchester and by Carl Sandberg and by Robert Remini.
Political thought: books like Witness, The Road to Serfdom, anything by von Mises, The Suicide of the West, Kevin Phillips' early books like The Emerging Republican Majority, nearly anything by Tom Wolfe.
Villains whose example is to be avoided: secularists generally, John Dewey, Adolf Hitler, Josef Stalin, Mao Tse-Tung, anything opposed to Francisco Franco in Spain.
Heroes to be emulated: The foregoing list of good popes, St. Maria Goretti, St. Benedicta of the Cross (nee Edith Stein), St. Pio, St. Maximilian Kolbe, St. Jose Maria Escriva, the four horsemen of SCOTUS, Sen. Henry Cabot Lodge the Elder (Wilson's enemy). Francisco Franco, Konrad Adenauer, Charles deGaulle, Ronaldus Maximus, Margaret Thatcher, Winston Churchill, Tony Blair, Dietrich Bonhoeffer, the ten Booms, Russian Orthodox martyrs to the soviet coup, Spanish martyrs to the communist and anarchist "Spanish Republicans," Nguyen Cao Ky, Ngo Dinh Diem, Menachem Begin, Jonathan Netanyahu, George S. Patton, Jr., Douglas MacArthur, the National Guardsmen at Kent State (5/70), Sen. Joseph R. McCarthy, Sen. William Jenner, Sen Henry Dworkin, Sen. George Murphy, Sen. Peter Dominick, Cong. John Ashbrook, Cong. Henry Hyde, Cong. Chris Smith, Cong. Curt Weldon, Prof. David Nelson Rowe, Prof. Clarence Manion, James Burnham, Frank Meyer, Willmoore Kendall, Will Herberg, Phyllis Schlafly, Janice Rogers Brown, .
Leave out the 20th century???? Hell, no. More like: Never forget the 20th Century and all of its examples positive and negative.