bum

Someone who frequently and consistently makes minor mistakes. They can be harmful or harmless, but they tend to provoke fierce criticism by other people. A bum may also consistently do harmful things as a joke, oblivious to the obnoxious nature of their actions. Bums often lose important items at inopportune times, and they are always showing up late to meetings.

"Aidan, you lost the receipts we gave you? You bum!"
"The bum Matthew is cheating again and he won't apologize."
"Max didn't submit the grant application on time? That bum!"