From what I can tell, most terrorists want to achieve a more specific goal than just to maximize civilian damage. Here are some groups which are called terrorist organizations:
Earth Liberation Front: carries out property damage related to fur farming, meat packing, GMO research, logging, etc.
Army of God, a Christian anti-abortionist group: kidnapped a doctor who performed abortions, and his wife, murdered or attempted to murder abortion providers, and carried out clinic bombings and arson.
In both cases the goal was to increase the perceived costs of respectively exploiting the environment and carrying out abortions.
What is the difference between a targeted murder of a foreign scientists by the CIA and a targeted murder of an abortion provider?
(I use "murder" because I think "assassination" is a fancy name partially meant to justify murder as an aspect of state power.)