> There’s no such thing

This is your opinion. I have worked with and managed 'toxic' employees. They are very much a thing.

There very much is such a thing, and they provide an accurate definition of it in their comment.

...what? It's not a claim to be falsified, it's a hyperbolic metaphor. I don't particularly like it either as it's been thrown around so much as to have lost much of its meaning (like "gaslighting", "gatekeeping", "narcissistic", etc.) but it's absolutely a thing. If you call a coworker who doesn't perform while falsely accusing you of incompetence in public Slack channels "toxic" then everybody knows exactly what you mean.

> It’s an unfalsifiable claim.

It is very falsifiable. Take that employee out of the team and look at the outcome.

You’re naive. God bless you for not encountering one of these people.

People like this are masters at working the system and will make everyone around them miserable. They crave attention and love to wield power.

The most toxic person I can think of spent most of his career broadly filing complaints for various forms of discrimination, which insulated him from accountability because any attempt to fire him would be seen as retaliation. His parting shot was to call the FBI and accuse a coworker of trading illicit porn on his work computer.

Nasty, evil people exist.