Barbaric, merciless (5)
I believe the answer is:
cruel
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">barbaric</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >'<span class="explanation-format__original">merciless</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for cruel that I've seen before include "Deliberately and pitilessly causing pain" , "Merciless" , "Heartless" , "Vicious" , "Painful" .)