a coldhearted person 或者 a heartless person
coldhearted：
Remember, some pretty girls are coldhearted when it comes to boys.
记住，有些美女在对待男孩的时候很冷血。
That was a practical, if coldhearted, calculus in a city like New Orleans.
如果心够硬的话，在新奥尔良这样的城市这是一个实际的计算问题。
Hastings' decisions may have seemed coldhearted, but ultimately they were proven correct.
黑斯廷斯的决定可能看起来冷酷无情，但最终被证明是正确的。
heartless：
You can play a heartless game using your keen intellect, charm and sex appeal to your advantage.
你可能会利用你的才智、魅力和性吸引来玩一场无情的感情游戏。
Don’t forget that winter is not only about the cold and heartless Snow Queen; it is also the time of Santa, his faithful deer, and funny elves.
不要忘记，冬天不仅只有冷酷无情的冰雪皇后；它也是圣诞老人、他忠诚的鹿和滑稽的精灵降临的时节。