rotten to the core
Thoroughly bad, as in It seems that this police unit is rotten to the core, involved in numerous extortion schemes. The noun core here denotes the central part or heart of anything or anyone. The idiom was first recorded in 1804.
Words nearby rotten to the core
rotten,
rotten apple,
rotten borough,
rotten egg,
rotten ice,
rotten to the core,
rottenstone,
rotter,
rotterdam,
rottweiler,
rotund