When looking for synonyms for the word "cruel-hearted", there are several options available to choose from. One could use "cold-hearted" to describe a person who lacks empathy or kindness. Alternatively, "heartless" and "callous" both convey a sense of indifference to the suffering of others. Another option could be "vicious", which suggests a deliberate intention to cause harm or pain. "Brutal" and "savage" both imply a level of violence or aggression. Ultimately, the choice of synonym will depend on the context and desired tone of the writing, but all of these words capture the essence of someone who exhibits a lack of compassion or kindness.