If you want to talk about left-wing terrorism vs right-wing terrorism... there is no contest... simply check wikipedia:
The wikipedia article for Left-Wing Terrorism in the united states consists of a single paragraph ending with:
(...) After 1985, following the dismantling of both groups, one source reports there were no confirmed acts of left-wing terrorism by similar groups.
The wikipedia article for Right-Wing Terrorism in the united states consists of 5 paragraphs ending in a list of 38 items since 2003, mostly murders and mass murders:
See also:
Domestic terrorism in the United States(...)
New America's tally shows that
since September 11, 2001, incidents of right-wing extremism have caused 86 deaths. Incidents causing death were:
(...)
(check link if you care)