Skills can be taught but attitude hardly changes

One of the worst people I've ever worked with was a guy who knew our system in and out, was a quick learner, and met all his goals in a timely manner. He was also the meanest person I've ever met and once threatened to punch me in the nose for not saying hello to him.

Yes

Luckily, I got the perfect mix! I'm currently working in a group with 3 other people who have absolutely 0 skill we can use for the project AND have a problematic behaviour. Luckily the other 2 are nice, logical and efficient so we get shit done while the others are doing poorly stuff we have already done or don't need.