- Someone who has no clue. This is rare but it does happen. I have seen some fly through interviews and then literally do nothing until they leave for another company as we are set to fire them.
- Assholes. Everyone is nice in the interviews. Not everyone is nice during code review. There is a sub-archetype of asshole called The Complainer. They can live in pairs, but if there is no Assholes, a true Complainer will find a way to turn someone into one. They are two sides of the same coin.
- My way or the highway types. Your team uses Design Patterns and Unit Testing. Bob says that is overengineering and refuses to be a team player.
Interviews focus on the first one, which is honestly simple for a relatively experienced interviewer to weed out. I don't believe in 10X rockstar ninja programmers. Either someone has the ability or they don't.
The real keys to great hiring are good managers and cheap firing. Good managers are hard to come by, but they can be built fairly easily. Cheap firing is usually easy, if that is your goal. Some locales restrict this legally, but there is always a loophole.