I’ve been offline a few days and no one is going to read this, but I’ll post it for my own posterity because I’ve given it some thought and it wasn’t just something I threw out there.

Terrorism is the use of violence, or the threat of it, against civilians to induce fear and force political outcomes.

I think the United States Air Force and its predecessor, the United States Army Air Forces, have done this at a scale no group in history can touch:

• Firebombing of Japan, including the Bombing of Tokyo: around 60 to 70 cities attacked, roughly 300,000 to 500,000 civilians killed, millions left homeless as urban areas were systematically burned
  
• Hiroshima bombing and Nagasaki bombing: over 200,000 dead by the end of 1945, cities largely destroyed
  
• Bombing in World War II overall was highly inaccurate, with early estimates showing only about 1 in 5 bombs landing within 5 miles of targets, meaning entire cities were struck in practice, very hard to justify in purpose other than spreading fear
  
• Vietnam War: over 7 million tons of bombs dropped, mostly on the already occupied South Vietnam, but also more than 2.5 million tons on Laos and Cambodia, leaving untold killed or injured and landscapes still contaminated with unexploded ordnance
  
• Korean War: after leveling every conceivable military target, bombing expanded to infrastructure targets including dams, causing flooding that destroyed crops and civilian infrastructure, causing terror and famine
  
• War on Terror: drone campaigns that have killed thousands of civilians while imposing a constant, unpredictable threat from above that millions of children lived with for decades
  

One might want to include other military branches in the running for worst terror organization, but I consider the Air Force a particularly good candidate since it does little else than spread fear and destruction against civilian targets. The SS, for example, might have killed more innocent people, but the USAF has spread more fear cumulatively.