Perfect character for a drama series

by Isaac
(England)

Question: I'm making a drama series of a scientist who has a girlfriend and they are sent to study an artifact in space which ends up destroying the world that the main protagonist knows, including his girlfriend. But he doesn't die because he gains immortality from that encounter.

After the world is destroyed our main protagonist wonders around the universe, until, many decades later, he is rescued from another civilization very similar to ours.

He is not very brave, and is afraid of pain, both physically and emotionally. I also wanted him to gain some sort of trauma by wondering around space for centuries, but I'm not sure how to do it.
This new civilization also enters in contact with this artifact, and their planet is destined to destruction.

The protagonist is then almost "forced" to become the hero of that new world by destroying this threat with help of his immortality and knowledge.
He also ends up meeting another girl, not very similar to his ex-girlfriend, but they end up doing pretty well. and the protagonist doesn't want her to die like his ex did, later in the story he stops being a unmotivated, scared, pussy scientist, to become a hero.

So, how should I build this character? His personality, habits, looks, etc? And the before-after?

I would like him to change over the story, but not too much. Not sure how to do it..
Its a drama, since the hero can actually save the new world, but it ends up being destroyed by another factor, and he once again wonders around space, with his soul empty like the black space around him

Answer: To build the character, start by listing all the things you know about him, including all the things you want him to do.

Then create a list of questions--any and all questions--about him. What don't you know about him that someone might wonder about? Remember to ask why he does the things he does and what that says about the kind of person he is.

Even seemingly innocent or mundane questions can matter a great deal in this exercise.

Once you have your list of questions, go back over them and jot down all possible answers for each question.

Take the best answers to these questions, the ones that work well together, and use them to create an expanded character sketch. You will likely have to make some alterations to eliminate any contradictions (bearing in mind that sometimes people don't behave consistently).

Once you've done all this, feel free to repeat the process. Take your current character sketch and create a new list of questions--all the things you still don't know.

I doubt you will need to do more than three rounds to get a very detailed understanding of this character.