What would you do in this situation...?

If he is armed with a rock salt slushie and serinading by Kurt was the concludion then i'll take it :) (glee fans will understand)

turen in to a werewolf and kill him

One problem-I don't know who I hate that much. *thinks* I got it! *SPOILER ALERT* The Styx! More precisely, the Rebecca twins. I freaking HATE them! I'd scream for Drake, Elliot, Will, or Chester, then assuming they heard me. I'd get a gun from one of them and attempt to kill the twins, though they might beat me to the punch.

Use time-control and take the weapon out of his hand and get a bazooka and shoot launch it times 10 in his face without hitting him. (The bazooka shell will be around his body) And then leave momentarily and start up time again. And watch his body get destroyed and when his body reconstructs then I'll take him and gag him and drop him in the middle of the Indian Ocean not without dismembering him and taking out his eyes and then I'll wait for the sharks to eat him.

He reconstructs his body again and this time I'll be sure to drop him to drop him in a volcano and when he does it again I'll repeatedly do brutal things to him. He won't die but I will make his many lives a living hell.

Run and find some wepons and then have a fair fight with that bastard...I would proberley lose but hey, I would do anything to hurt that bastard personally for what he did to Rue\Katniss\ Peeta\ etc.

do what Isaac dose, cry until it goes away

I don't loath any fictional character.