How do I remove the Enderdragon from the normal world?

So I accidentally spawned the Enderdragon in my normal world using the Single Player Command "spawn random". Can I use any single player commands to remove this Enderdragon (or is there any other way)? It is currently destroying all my hard earned creations.

If you're on Minecraft 1.8 or later, you can remove the dragon fairly easily. This actually won't kill the dragon, but rather delete it outright (which means it will not drop a portal).

/kill @e[type=EnderDragon]

If that doesn't work, you can do this instead:

/gamemode c
/give @p diamond_sword
/effect @p 5 60 255

… which switches you over to Creative, gives you a diamond sword and a ridiculous damage buff. Fly up to the dragon and bonk it with the sword, then clean up the End portal it drops.

Also, if you already have Single Player Commands installed, then you can do this easily using the commands it provides.

• /killall EnderDragon will delete the dragon from the world.
• /killnpc will kill all NPCs in a certain radius around you, including the dragon. Note that this will trigger the death animation and cause a portal to the End to spawn.