Consider the case where a professor is erasing a board and one of the teaching assistant tries to help him by erasing part of the board.
Unfortunately, while trying to pick up the eraser, the teaching assistant bumps into the professor and they both drop their erasers.
An outside observer sees this and says the TA is ______, rather than helping.
The missing word or phrase would capture the good intentions but also express the fact that the intended help had the opposite of the intended effect.
In Mandarin Chinese, the phrase
帮倒忙 comes to mind, but the Google translation "disservice" does not quite capture it.