coldest line in all of arrow?

my personal take, near the end of season 5 in a flashback scene between anatoly and oliver

Anatoly: This is not human, tough man.
Oliver: Actually he gave it up pretty quickly, the rest was for fun.

a scene of oliver torturing a guy for FUN, this really made me realize how easy he goes on his enemy's in the show, even in season 1 where he kills, he was still hiding his true abilities