心 (xīn): Heart, mind, or core. In this context, it refers to a person's nature, intentions, and thoughts.
狠 (hěn): Vicious, ruthless, cruel, relentless.
手 (shǒu): Hand. This represents a person's actions, methods, and deeds.
辣 (là): Spicy or hot, like a chili pepper. Metaphorically, it means harsh, severe, painful, or stinging.
These characters combine literally to mean “heart is vicious, hands are spicy.” This creates a powerful image: the malicious plans are formed in the heart (心狠), and they are executed with painful, severe methods by the hands (手辣). The two parts reinforce each other to describe a complete and active form of cruelty.
Describing Villains and Criminals: This is its most common usage. In movies, TV dramas, and news reports, villains and criminals are frequently described as 心狠手辣 to emphasize their evil nature.
In Arguments and Accusations: In a heated personal dispute, someone might use this term to accuse another of being incredibly cruel and manipulative. For example, “I can't believe you'd spread those rumors just to get a promotion. You're truly 心狠手辣!” It's a very serious insult and not used lightly.
Business Context: While less common, it can be used to describe a competitor who uses unethical and vicious tactics to destroy other businesses, far beyond simple competition.
The connotation is always strongly negative, and while it can be used in both formal (news, literature) and informal (gossip, arguments) settings, its weight and severity remain constant.