Noun
change agent (plural change agents)
(business) A consultant hired to assist with implementing changes in an organization's structure or operations.
Death is very likely the single best invention of life. It is life's change agent. It clears out the old to make way for the new. Steve Jobs
The cool part about working for Disney is that they've allowed me to be a change agent. Christy Carlson Romano
Governments cannot make marriages or turn feckless individuals into responsible citizens. That needs another kind of change agent. Jonathan Sacks