Identify the group that worked to improve the lives of industrial workers.

Rather than a particular group I would say that with a lot of evidence to back it up that labour unions have since their inception been used to improve the lives of industrial workers, at least on the job. For example, as far back as the 1500's, at least for awhile, the Knappschaft union of the German miners in the Erzgebirge rich silver mines even won an 8 hour day and indemnity for the widows of miners killed in the mines.