Prove it

Worst what?

Off the top of my head.
1910s - WW1 (biggest pointless war in history), Spanish Flu kills millions, large swath of depressing poetry and novels as youth of the developed world is crushed, Armenian genocide, Piltdown man, Birth of a Nation, lynchings, chemical warfare, Daylight Savings Time
1920s - hyperinflation in Germany, start of Depression in Europe, civil war in Russia/Soviet Union, Volstead Act, polygraph, Mussolini, Teapot Dome, Scopes Trial
1930s. Stalinist purges. Ukrainian famine. Kristallnacht and Nazism, Rape of Nanking and invasion of Manchurian China, Chinese civil war, Smoot-Hawley, Global Depression with two phases in America, invasions of Poland, Czechoslovakia, and Ethiopia, Spanish civil war, Hindenburg, Munich
1940s - Roughly 80 million people die in a global war, use of atomic weapons, massive destruction of civilian infrastructure in Europe and Asia, beginning of the Cold War, Berlin Blockade, Gandhi assassinated, Huey Long, Mao wins
1950s - Hungarian revolt brutally suppressed, Korean War, Yankees peak of dynasty, McCarthyism, Elvis, Great Leap Forward, Castro
1960s - Vietnam, JFK assassinated, Cuban Missile Crisis, Berlin Wall, Cuban hijackings, Six Day War, MLK assassinated, inner city riots as Civil Rights gets messy (finally), Charles Whitman and Manson, Cleveland River catches fire, George Wallace
1970s - disco, Watergate, Cambodia/Khmer Rouge, War on Drugs goes into full bore, Vietnam still, 3 mile island, Love Canal, Kent State, Iran goes Islamic, Munich (again)
1980s - apartheid (actually ongoing, but finally peaks into a global issue), peak of bad hair and clothing for the century, ongoing Cold War, Falkland Islands/invasion of Grenada, Nicaragua and Panama get messy, Iran Contra, S&L crash, Exxon Valdez, cocaine, new Coke, John Lennon killed, Reagan and the Pope shot, San Francisco earthquake, AIDS, invasion of Afghanistan, Beirut, Bhopal, Chernobyl

I can obviously find a number of problems with this declaration even comparing it to the last century. If you want to go back to eras when Genghis Khan was on the march, slaughtering entire cities and catapulting plague victims into besieged towns, or the Black Death, the vast and expansive rape of American (and African and Australian and Pacific Islander) aboriginal peoples/territory by Spanish conquistadors and other European settlers, slavery, the American Civil War, the Opium Wars, the closing off of China's vast navy, the Dark Ages, the Roman Empire (especially post Aurelius), the Spanish Inquisition, the Pequot War, the Crusades, witches being burned at the stake, torture devices that make waterboarding seem like a pittance. Even taking this at a face value that it was somehow a terrible decade for AMERICANS (and obviously you have discard the fact that it was probably a very good decade to be an Indian or Chinese or Brazilian or Indonesian), I still don't see how it was the worst decade to be an American ever. 1860s looks pretty bad. 1850s looks bad. 1830s looks bad. 1810s looks bad. 1870s and 1880s have some big downsides to go with the vast increases in wealth, technology and living standards. 1930s for America makes this look like a picnic economically. While there are plenty of ways to make it seem like this was just as bad as the 1930s, it isn't even close and that decade ended with war again on the horizon. Calling this past decade "peaceful" or with a supposed "absence of war" is a joke. Both the 1980s and 1990s are far more "peaceful" by my reckoning, despite invasions and meddling in the Middle East, Latin America and Europe, just like now. But the mere presence of a war, with all its attending casualties and destruction is not a sign of terribleness. Because wars have been much worse and much more lawless and reckless in destruction and death in our history. Finally, while you can complain about the plight of workers and stocks all you want (even though we're still not sitting anywhere near 1930s levels of insanity and despair), the fact is that many workers are not ENSLAVED as they were for a large portion of American history, that mothers and children do not die in childbirth or infant mortality, pollution is nowhere near as bad as it was in the 19th century or much of the 20th (we haven't had any rivers catch fire for example).

I could go on, but all I'm seeing is our tendency to look at the present as though the past doesn't exist for our comparisons. All things in the present are therefore the best or worst. It's not enough to simply have a marginally good decade for most of the world. There's no story there I guess.

I suppose you could argue on balance that a comparison with only the 1990s, this was a terrible decade. For Americans. But this is 1) a distressingly narrow worldview and 2) not all of recorded history in which to attach the authority of "ever" to your conclusions and 3) not really that much worse than the 90s on balance. The WTC was attacked then too. We didn't have race riots, maybe Katrina counts here. There wasn't a genocide in Rwanda but there was one in Sudan. There was a scuffle involving Somalia in both time frames. There were no bad movies about Ebola, though we did remake just about everything else. There were school shootings in the 90s (Columbine) just as there were in the aughts (Virginia Tech). There was no Y2K or Mad Cow disease, though there is H1N1 and an ongoing struggle to get uneducated people to take vaccines seriously instead of celebrities. In my view, Viagra and Titanic pushes the 90s into the "that decade sucks too" category. Though Shawshank and the end of the Cold War (and apartheid) are pretty nice bonus points. And the first Gulf War was fun for the Air Force.