First off you must have a general vision of what fantastic things you want to recreate of your favourite character. Then you add more beautiful details to them that go unseen by the regular fanartists of that fandom.
Such as emphasis on expression! Be able to empathise with the character and also sympathise with what emotional trauma they may have had in the past.
Like Jin for example! He really did love his brother a little too much didn’t he? Now he’s a lovable yandere psychopath with a brother complex!
I have replicated an example for you to all follow.
The one on the left is wrong because it’s far too ugly and emotionless to be our beloved bastard for he is being far too subtle!
Now the right! Now that is a fine piece of absolute AGONISING INSANITY. I even added blood to leave an open question as to whether he’s a cannibal, vampire or has a stomach tumour!
Tutorial over! You all are now educated to break your fandoms!