Janeway did nothing wrong.
Tuvix was never meant to be, and cannot help the circumstances of his creation, but the needs of the many outweigh the needs of the few, or the one.
I wouldn’t feel good about it, as clearly Janeway did not, but I would make the same choice.
The way I see it, Tuvok and Neelix died in an accident, and a separate life emerged from it. The crew just couldn’t accept their deaths so they killed Tuvix to get them back.
I don’t see it as a logical decision but an emotional one. How Tuvix came to exist doesn’t matter, he was still a person, and they basically murdered him to get their friends back. He wouldn’t be the first living thing that wasn’t “meant” to exist.
Either way it’s a very difficult moral question and probably the best episode in Voyager as far as emotional impact.
