I've had my share of incompetent coworkers. In order of appearance:

1. A full stack dev. This one guy never, and I mean NEVER uses relationships in their tables. No indexing, no keys, nada. Couple of months later he was baffled why his page took ten seconds to load.

2. The same dev as (1). Requirement was to create some sort of "theme" feature for a web app. Hacked it by putting !important all over the place.

3. The same dev again. He creates several functions that if the data exists returns a view, and if it doesn't, "echo '0'". No, not return 0 or return false or anything, but fucking echo. This was PHP. If posted a rant about this a few months ago.

4. Same dev, has no idea what clean code is. No, not just reusable functions, he doesn't even get indenting right. Some functions have 4 spaces, some 2 tabs, some 6 tabs! And this is inside the same function. God wait until he tries Python...

5. Same dev now suggests that he become the PM. GM approves (very small company). Assigns me to travel to a client since they needed "technical assistance about the API". Was actually there to lead a UAT session.

Intermezzo, that guy went from fullstack dev to PM to sales (yes, one who calls clients to offer products) to business development, to product analyst in the span of two years.

After a year and a half there, I quit.

6. New company, a "QA engineer" who also assumes the role as the product owner. Does absolutely no tests other than "functional tests" in which he NEVER produces any form of documentation. Not even a set of test cases. He goes by "intuition".

7. Same guy as (6), hands me requirements for a feature. By "hands me" I mean he did that verbally. No spec documents, no slack chat, no Trello card. I ended up writing it as a card in Trello. Fast forward to the due date, he flips out because that wasn't what he wanted. Showed him the card. He walked away, without thinking of a solution how this mess should be handled.

Despite all this, I really don't want him (6&7) to leave the company. The devs get really stressed out at this job and he does make a really good person to laugh with/at.