“YOU LACK CONVICTION.”
This is a magnificent scene.
1) Because Coulson, period.
2) Because he figures Loki out first. “You lack conviction.” Loki lacks certainty on a deeper level. He lacks certainty that he is right and that this is what he wants, and he lacks a real moral grounding on which to fight for his cause. He has double-thought and deceived himself into thinking he is some dark savior. Deep down he still thinks he is the blue skinned monster that his family could not possibly have ever really loved. Put simply,Loki doesn’t even know what he wants. If he wants to win, WHAT he wants to win, HOW he wants to win it. He has this myopic determination, but that’s just a coping mechanism for being as internally confused as he was in “Thor.”
3) Coulson recognizes this RIGHT AFTER HE WATCHES THOR AND LOKI INTERACTING, and sees the “fun of it” leaving Loki’s face once he’s dropped Thor out in the metal death trap. Because Thor stopped fighting, and LET Loki drop him out that metal death trap. Because Thor knows Loki needs to feel like he’s won. Like a heartbroken child that needs to feel validated, even in the most twisted way. (If you don’t believe me, just look at the gifs of Thor’s face and the way he leans back from the glass and just stands there frowning in confusion, and, then, disappointed resignation).
4) THE FACT THAT LOKI NEEDS TO PAUSE TO JUSTIFY HIMSELF TO COULSON, A MERE “ANT,” WHICH GIVES COULSON THE OPENING TO SHOOT HIM, PROVES THAT COULSON IS RIGHT. LOKI IS INSECURE IN HIS MISSION AND ITS SUCCESS, AND SO HE HAS TO MANUFACTURE THE BOMBAST AND THE DEFENSIVE WORDS TO MAKE HIMSELF FEEL BETTER AS MUCH AS TO PROVE HIS ENEMY WRONG. Magnificent writing.