cold-blooded

• (US) IPA^(key): /ˈkoʊldˈblʌd.ɪd/

cold-blooded (comparative more cold-blooded, superlative most cold-blooded)

1. Having an unregulated body temperature; ectothermic.
2. Lacking emotion or compunction.
   • 2017 July 16, Brandon Nowalk, “Chickens and dragons come home to roost on Game Of Thrones (newbies)”, in The Onion AV Club‎:

     That’s what it looks like Arya’s planning to do at the campfire. For much of the scene, she’s weighing her options. She could take those guys. She could get to them before they got their swords, and she could swipe their gold and their meal. It would be something like what the Hound did to those peasants. At the time Arya was upset at him for it. But now Arya’s a cold-blooded killer.

• (lacking emotion): sangfroid, reptilian; reptitious (obsolete)

• warm-blooded