Symptoms of the Darkside are listed below:

1. Red lightsaber

2. Yellow eyes(in some cases)

3. Deformed face/body

4. Force lightning

5. Force choke

6. Urge to kill all Jedi

7. Urge to rule the galaxy

8. Darth as a first name

9. Dark clothes

10. Pale skin

11. Foreseeing things and telling everyone how it's just like you foresaw it

12. Overconfidence

13. Dieing in an overdramatic/cool way (you can come back there's always the EU)

14. A need for the Imperial March to play when you arrive

15. Dramatic entrance (this goes with #14)

16. Loss of limb(s)

These were the ones that I could think of, if you know of any other symptoms comment please. We must inform the galaxy of this horid thing. §