Green Lantern himself!

Stewart stood before you in his hero's uniform, arms folded with a stern look. You mentally transfer all of your anxieties flowing through you to your hands, squeezing them tightly into fists, and you try to don a determined mask. "Lantern," you greet plainly.

"Listen. Supergirl told me that you've been under Batman's command." He puts his arms down and continues, "Take it from me, kid: give all you've got, then give more. Put your all into what you do."

"I gave my all for three days for this intense regimen, and I intend to continue giving it what I've got." Then John... smiles? And he seems to switch topics on the fly.

"Being in the military taught me about responsibility, such as taking it for your actions." You could only watch as he approached you, dumbfounded as he holds your shoulders in his hands. "I appreciate you being upfront with me about what happened. And this will serve as payback for screwing Mari. If you survive..." Those words along with his devilish grin made you shake to your core, and you would be scared for the rest of the workout. If John didn't start chuckling. "Just messing with you, kid."

He walks off, still chuckling, and after you regain your senses, you shout to him, "Not funny, man! That was not funny!"