No right wing antifa? It doesn't bother you that the vast majority of "political" murders are committed by white nationalists?
This all depends on when you are counting from and where you are counting.
Start counting JUST the USA AFTER Sept 11th, 2001? Sure, political murders by Islamic Extremists are not going to top your list. But White Nationalism may not either, depending on how you classify some Anti-Semitic attacks. White Nationalism definately has a Anti-Semitic flavoring, but the question remains whether all Antisemitism is White Nationalism. Certainly, some recent antisemitic attacks were committed by African-Americans, generally ruling out White Nationalism as a cause.
Start counting from June 12th, 2016? Islamic Extremism is back on top with Orlando nightclub shooting.
Start counting AT 9-11? Islamic Extremism on top.
Counting the entire world? Starting when? High scorers include the Mass Killing of Landlords and the Cultural Revolution, the Holocaust, the Holodomor, genocide of the Poles 1941-1945, The Three Alls Policy, The Cambodian Genocide, The Rwandan Genocide, the Armenian Genocide, The Conquest of Algeria, The Partition of India, The Great Purge of 1936-38, The Greek Genocide of 1922, Soviet killings of Poles 1937-38, The Occupation of Tibet, Destruction of Kurdish Villiages in 1991, the Al-Anfal Genocide of 1989, War crimes by the Syrian government during the Syrian Civil War 2015-2019.
Basically, your highest scorers for political killings are Mao, Hitler and Stalin. Since Mao and Stalin can both be counted as Communists, the Communists have officially racked up a higher death toll worldwide and throughout history than either White Nationalists or Islamic Extremists.
If we are looking at prevention, which is what we should be doing instead of trying to figure out which ideology is the worst, we should look at what all these have in common. The one thing that they all have in common is that they were committed, by definition, by politically motivated individuals, either in or out of power. The worst type of person in the world, hence, is a politically motivated or invested individual.
In order to protect the innocent, I would suggest rounding up all individuals who are either in elected positions, or have run for elected office, or are politically invested in some way, i.e.: people who read or post on internet political forums, or read or write political books or articles that paint some other political ideology as "bad", and have them all shot. Failing this, these individuals should be stripped of the capability to serve in office or vote for elected officials.