Is there any justification for the Reign of Terror in France (1793-1794)?Does the end justify the means?
No, there is no justification for the extreme actions that were taken by the revolutionaries during the Reign of Terror.
It is perfectly understandable that revolutionaries would worry greatly about counterrevolutionary activity. It might even be acceptable to jail or exile people who are a serious threat to a revolution (let us assume that the revolution's ends are good). However, the relatively indiscriminate violence of the Reign of Terror was beyond the bounds of anything that could be acceptable. It was surely not necessary for the Revolution to kill tens of thousands of people.
The end may justifiy some means, but no end can justify this much killing anywhere other than on the battlefield.