How to kill the big green monster in Magicka?

Lightning, Arcane, Cold - Freezey shocker beam o death!

Check this out, http://forums.steampowered.com/forums/showthread.php?t=1733437

Lightning + Arcane -> Target -> Kill :D

I assume you mean the troll? You don't even have to kill the first one...You can walk right up to it, and examine the moose he's eating. But if you do hit him, he'll attack, and you'll be in trouble.

Here is a spell for you, memorize it and you will conquer...BEHOLD THE MIGHT OF:

SQFQFAA

Arcane+Steam+Steam+Lightning+Lightning=the most destructive beam attack in the game. Practice it, and you will turn huge slow moving monsters into paste. You can also use it as an AoE, and it excels there as well. Put it on your weapon! It's good there too! It slices, it dices, it chops!

Generally if you are quick enough, you can kill pretty much anything in the game 1 v 1 if you make it wet then ice it. From that point on, just hit it with any spell that includes ice and it will maintain the frozen status no matter what other damage you hit it with, unless you hit it with water/steam/fire.