Aviation unions force very high standards and represent a lot of the developments in safety and procedures.
Nuclear power is heavily unionised, resulting in a very stable and highly qualified workforce.
Unions in film and tv have done great work defending artists rights and protecting actors, writers, crew, and others from predatory behaviour by studios.
Fire fighter unions stand against unsafe demands and protect the crews in ways the individuals can’t, resulting in meaningful change. (I’m aware of UK but projecting and assuming this applies internationally)
I could go on…