Power's character Cameron Murray is currently under pressure to buy Carl's silence, after the scheming businessman uncovered his affair with Chas Dingle.
Next week's episodes see Carl (Tom Lister) continue to harass Cameron for the cash. He even shows no mercy when doctors reveal that Sarah - the daughter of Cameron's partner Debbie - is developing leukaemia.
Power told Inside Soap: "What's so alarming about it is that Carl seems to have no sympathy for Sarah's illness whatsoever. Cameron is shocked that a human being can be so evil and callous at what is such a painful time.
"Carl wants his cash, and he moves the goal posts from one moment to the next. Cam gives him money, and then he wants more. He seems to like playing these mind games.
"Carl keeps sending Cam threatening texts at the worst possible moments, and that makes him so angry. Cameron always knew Carl could be a menace, but he never knew he could be this malicious. This shows how purely evil Carl King really is."
Emmerdale airs weeknights on ITV1.