Especially regarding unions in government - they not only cause inequality, they cause corruption and the decline of the rule of law and the rise of tyranny.
Personally, I don’t think Unions cause inequality among the rank and file members. They are all screwed collectively by their union leadership who are nothing more than crooks in suits.
If anything Unions serve to EQUATE humans to a Union define service grade which the union bosses dictate and from which collect their filthy lucre.
And add to this unions in education. The union movement is directly related to the fall of a once great public education system.
When you have the young and learning at your mercy and at the same time you subscribe to a system of pay for time in the position (rather than pay for merit) you end up with a country that does not understand the concept of merit while pretending to believe in the concept of fairness (when nothing is fair) and equality (when equality does not exist either.)