Power hungry bottom feeders

"Doctors saves lives and lawyers are nothing but power hungry bottom feeders"
This is the quate from one of my favarite American drama "Suits".

This is a scene where Jessica Pearson who is a managing partner of Pearson Spector Litt conveyed her decision about career to her father Allen Pearson who is a doctor and this is what Allen said to her.
He raised his daughter and wanted her to be a doctor just like him but her choice was different and he clearly had nothing but contmpt for his daughter's career choice.

I could learn a new idiom, the meaning and how to use it.
More than that, this idom made me realize how to learn English and what to write here.