Oh don't get me wrong, he still clearly executed those guys. It's just that their presence with Blood in Blood's office infers they're members of the conspiracy and likely bodyguards, and they do fight back. It's an impossible fight, but there's still a stronger ambiguity to the scene than Malcolm's kills; the Dark Acher was introduced murdering a unarmed man and escalated to killing scientists and former partners, and he reintroduced himself in season 2 by murdering another associate! And when I say Sade inspires fear, I don't mean pants wetting terror, but Sara definitely was frightened of Slade when she heard his voice. Confronting an opponent head on is something these guys are used to. Knowing their enemy has a clear chance at murdering a loved ones before they can do anything scares them. Roy's clearly worried about Thea too, but once he gets a chance to possibly defend her, he calms a bit. And Ollie has the balls to try and prison shank Slade in the eye, but you feel his terror when Slade has his hands only inches from Moira's neck. Fighting and dying against an opponent is one thing; knowing an immortal killing machine wants to destroy your family is another.