[t43562]

Bad developers write code that has a negative impact on team prouctivity. e.g. by insisting on a wildly overcomplicated implementation or writing poor tests and being aggressive to anyone that questions them, or being highly negative about some decision or other to the point where the team are not sure if that person is in charge or their manager is.

They can also pester everyone with mountains of trivia in PRs and refuse to change anything in their own and so on and on.

My own boss says "the main thing is to hire nice people - everything else can be improved" and that changed my perspective a lot. I think he's right.

A bad EM can do more damage of course. :-)