i know of a scenario in which multiple employees were making $100,000 as unioned employees. they were on a full-time schedule, aggressively arranged by the union, that allowed a certain percentage of work time to be from home. the result of these employees? they lied about their work, "worked" almost exclusively from home, and had less than 5% of the work output of the non-unioned employees who had the exact same titles and job duties who also happened to make less.
it took many years (years!) to get rid of these employees (basically through forced retirement) and any attempt to have the employees to have even a minimally acceptable work output resulted in angry visits and process blockages from the union. the managers reporting the fraudulent behavior and giving the poor ratings were harassed, and the union straight up lied to the point where the managers started recording all conversations and actions with the unioned employees and union representatives to even protect themselves and their jobs (as non-unioned employees and managers!). the employer was basically powerless in getting literally ANY work from these employees, who acted as a tumor in the organization. because of the aggressive and firmly established union, these employees essentially committed theft and fraud as their full-time jobs while making six figures.
so no. unions are not always these powerless little entities getting stomped on by corporations. as the person you replied to stated, BOTH sides can often be viciously ruthless and blind in their quest for money and power over the other.