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 the development snapshots leading up to it), 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).
If that doesn't work, you can do this instead:
... which switches you over to Creative, gives you a diamond sword and an 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.