Tā duì biérén de tòngkǔ mámù-bùrén, lìngrén hánxīn.
His insensitivity to others' suffering is chilling.
Tips
memory
麻木 (numb / paralysed) + 不仁 (without benevolence / feeling). Originally a medical metaphor: 仁 can mean the sensitivity of flesh. Someone 麻木不仁 has lost the ability to feel - physically or emotionally.