The last Olympics that witnessed terrorist violence was 1996 Atlanta Summer Olympics when an American terrorist Eric Rudolph exploded a pipe bomb in Centennial Park killing a mother and injuring 100 people attending a free concert. The bombing was condemned by the then U.S. President Bill Clinton. Local terrorist groups (both lone gunmen and KKK) have been a headeache for state and US governments long before Al Qaeda. Major bombings in the US against abortion clincs or other buildings are usually carried out by American terrorists.
Prior to Atlanta, the most horrific terror attack at any Olympic Game was the 1972 Munich Massacre. Carried out by a squad of Black September militants. This was decades before the term terrorist began to be use loosely for any type of political violence: resistance or revolutionary. Black September was formed by Palestinians in 1970 who were first expelled from their homeland Palestine in 1948 who grew up in refugee camps in Lebanon and Jordan. Prior to Munich Olympics Black September had planned to overthrow the Hashmite government in Jordan leading to the Black September conflict between Jordanian government and military forces to remove the Black September Organization from Jordan altogether. It also led to expulsion of Palestinian refugees from Jordan. Lebanon continues to running into similar battles between Lebanese military forces and Palestinian militants in the 50 year old refugee camps across Lebanon to this day. Black September, PLO and Fatah had long lamented that the world had forgotten the Palestinian refugees since 1948 while supporting Israel and its security first. Israel had a carte blanche then as now to fight terrorism reminding the world that its borders were threatened by all its neighbors.
Seconds from Disaster: 1972 Munich Olympics
Security at 1972 Munich Olympics was blamed as a major factor in the Munich massacre. In 1972, no Western nation or any country around the world had any specialized counter terrorism forces or special security forces to handle the violence that occured at the Munich Olympics. The invasive war on terror security measure and policies that exists across the world today including putting counter terrorism forces on standby at the Olympics and other major sporting events would've been met with horror in 1972. While Russia stresses over security, 1970s Germany had wanted to showcase to the world that it had changed and was a friendlier and inviting country since it lasted hosted the Summer Olympics under the Nazi regime. Adolph Hitler used the 1936 Games as propaganda to promote the so called might of Nazi Germany. German police were laxed with security in and around Olympic village allowing athletes and visitors alike to come and go as they pleased. It was said security was so laxed that people were sneaking into the Olympic village. The lax security tragically benefited Black September terrorists who held eleven Israeli athletes hostages on live TV for days before they were tragically killed along with 5 Black September terrorists and a German police officer in a failed rescue attempt by Germany security forces. Following the Munich massacre, Western countries and the world reviewed methods and policies to prevent future terrorist attacks against athletes including the creation of many modern counter terrorism forces. Sadly Israel lost nearly its entire Olympic team at Munich. Out of the 15 Israeli athletes sent to Munich, only 4 came back to the country. One of the surviving 4 athletes Shaul Ladany (today a professor at Ben Gurion University) had survived the Bergen Belsen Camp as a child and returned to Germany as a race walker on the Israeli team. Israel's revenge against Black September also extended to other Palestinian militant groups. The Palestinian refugee dilemma that had gained worldwide sympathy from anti colonialist forces and peoples was crushed by the 1972 Olympics. The 2012 London Olympics occuried without any security breach but was noted for the 24 hour security forces and camera equipment surrounding the Olympic village and British soldiers sitting in on some games. As the world's eye focuses on Russia and the raging insurgency in North Caucasus, Russian security is scrambling to find the lost black widows and keep the militants from carrying out their attack before the start of the Olympic games.