The loan shark would leech off of Frank's desperation with absurdly high interest rates.
Verb-Noun
Group
Dishonest
Joan loved Barry, but because he never worked and just played video games all day, she was concerned that he was just a leech and didn't really love her in return.
Socialists say that capitalists are leeches and exploit the working class who do the labor, and capitalists say that socialists who want to take their hard earned dollars are the leeches.