Underperforming is not about making mistakes. It is consistently being unable to learn and adapt. It is being unable to mesh with the rest of the team. It is feeling like "I wish I had not hired this person".

Also I think that different organizations have different thresholds for how much they can tolerate with an underperforming employee. In larger organizations, I have seen situations where an employee was not a great fit for the role they were originally hired for, but over time were able to move into a different role where they were effective. E.g. someone who can't write code to save their life, but is actually quite effective as a middle manager.

But in a startup situation where every new hire is going to make a huge impact on the team, and "money is running out" (as the article is titled), you might necessarily need to be less forgiving.

I don't think that a bad employee is someone that lacks experience. The article is not so clear on that point but I don't think it is what the author meant... That said, in my opinion, a bad employee is someone that gains nothing from experience and that is not going forward, and this can easily be detected after some time.

Are you saying that this guy should fall on his sword because he messed up once (and learned from it)? Or that, having messed up once, he's obviously not qualified to make firing decisions? I'm failing to find a charitable interpretation here that makes any sense at all.

Bad employees fail often, never try anything outside their comfort zone, and don't learn from their mistakes or take responsibility for anything. He didn't give an in-depth version of what he considered a bad employee to be, but it's fairly obviously implied by "not pulling their weight" to the degree that they eventually demotivate the rest of the team.

I wasn't being charitable; but I completely missed that he said "one of my earlier businesses" and read "one of my earlier experiences (in this business)".