But note that as far as the US is concerned, in the past couple of decades, right wing extremists have killed a significantly greater number of people than left-wing extremists (eg. the CSIS credits them with 90% of all extremist killings in the timeframe 2018/19). They also lead by number of plots - though by body count, Islamist terror still takes the lead for the obvious reasons.
"I am particularly concerned about white supremacist violent extremists who have been exceptionally lethal in their abhorrent, targeted attacks in recent years" said (now-former) acting DHS Secretary Chad Wolf in DHS's most recent domestic threat assessment.
