A waste of space
Definition 1 of 2
Pro Tip 1/3Negative Connotation
The phrase conveys strong disapproval and should be used carefully to avoid offending someone. 
When he failed to deliver on his promises again, his colleagues muttered that he was a waste of space.
Pro Tip 2/3Colloquial Usage
Mainly used in casual or informal situations, and rarely in formal contexts. 
In the staff room, they joked that the broken coffee machine was a waste of space.
Pro Tip 3/3Emotional Impact
This phrase can hurt feelings; use it to express frustration, but be cautious about the listener's emotions. 
Feeling down, she whispered to her friend that she felt like a waste of space.