If the keyword was ever profitable for you, find a way to optimize onpage elements and ad copy to be more closely tied to the keyword. Move the keyword to it's own ad group if you have to and create ad copy that uses that particular keyword.
If you have no intensions to improve your QS or increase bid, why keep the keyword?
I've never received a clear answer as to whether or not an inactive keyword could hurt a campaign, but I can tell you that it won't help you to have inactive keywords. I would, at a minimum, pause the keyword rather than leave it inactive.
In the former situation, I'd probably move them out, either delete them if they're not important or move them to another ad group if I want to rehabilitate them.
If the QS is OK and I just don't want to pay the price, then I'll likely leave them in there, because often in these situations it fluctuates between active and inactive. And if the QS is OK or Good, you shouldn't be hurting the rest of the group.