The Borg
As a collective they are, of course, horrible, committing atrocities throughout history on a level we probably can't even wrap our heads around.
On an individual level they're, by and large, people forced against their will to take actions they would never undertake, or even have the ability to undertake, of their own volition. Even when freed from the collective, which most of them never have the opportunity to experience, they will never escape the memories of their past actions.
I daresay they're even more sympathetic if you've read the novels and know the rather tragic story of their origin.
If the Borg are sympathetic (in canon) then so is NOMAD. Poor baby had an accident and just wanted daddy to make it all better.
I think we may be going a tad too far here. What's next, the Doomsday Machine?