He's always been in control. Always. It's something that was drilled into him from the very beginning. You have to control it, son. Do not let it control you no matter what. He never slipped up and took pride in that fact.
So why did this… this… this monster have to ruin it for him? Why did he get to muddy that clean streak for Marco? He was only supposed to use his bending for good dammit! The waterbender could feel his anger spike as he stared at the suspended attacker in front of him, strained gasps falling from their lips almost like music to his ears. He hated it; he hated this feeling of euphoric pleasure he got out of this. Was it always like this for others? Almost like a drug-induced high by controlling someone else through their blood? Marco's tongue darted out to wet his lips as he raised his hands and, in doing so, raised the attacker higher in the air.
To hell with it. This bastard hurt his friend. They hurt Jean. They needed to be hurt, too. They needed to know that it was wrong to mess with his friends and wrong to mess with him. He narrowed his eyes, focusing on the flow of the blood in the other's body and feeling it pump through their heart. Gotcha. Just a twist of the wrist and he'll teach this monster what happens when they mess with his Jean. No one will ever, ever touch-
A hand on his ankle stops him.
"Marco…Marco, stop."
He looks down to see Jean staring up at him with a multitude of emotions running across his face: shock, distrust, disbelief, and one that takes a minute for the waterbender to register. Fear. Jean was scared of him. That lone thought screamed in Marco's head, had him dropping the assailant as though someone had cut a puppet's strings and swallowed hard.
"J-Jean… Jean, I was just protecting you. He was going to-" The firebender waved his hand dismissively and grunted tiredly, rolling over onto his back and staring up at the cloudy sky.
"Don't. Just… just don't, man."