Question: [A while ago](https://writing.stackexchange.com/questions/36944/avoiding-darkness-induced-audience-apathy), I asked if there any possible way for my series to avoid causing [Darkness Induced Audience Apathy](http://tvtropes.org/pmwiki/pmwiki.php/Main/DarknessInducedAudienceApathy). A well thought-out response stated that unless I give my readers a reason to care about my protagonist, they won't give a damn about the conflicts he's involved in (due to his existential nihilistic worldview and selfish nature) and will [outright](http://tvtropes.org/pmwiki/pmwiki.php/Main/EightDeadlyWords) [despise](https://tvtropes.org/pmwiki/pmwiki.php/Main/BaseBreakingCharacter) [him](https://tvtropes.org/pmwiki/pmwiki.php/Main/DesignatedHero). 

What I forget to mention was that I plan having my protagonist undergo a character arc over the trilogy where becomes significantly less selfish and eventually abandon his nihilistic philosophy. It's also revealed through a series of flashbacks that his behavior stems from his early years where he was raised by abusive parents, forced to fend for himself on the streets, fell in with a gang of seedy people just to stay alive and was betrayed by someone who he was very close with. And unlike many fictional works that portray nihilism in a negative light, the protagonist's nihilism revolves around the fact that he believes that his life is meaningless due to lacking of clear purpose.

But when all is said and done, I feel that he's nothing more than a soulless archetype (along with every single character in my trilogy) and comes across as a grating character, despite having a good reason to justify his behavior. In short, how can I make my protagonist more likable and somewhat redeemable?

Answer: 
You say it yourself:

> 
> I feel that he's nothing more than a soulless archetype
> 
> 
> 

A soulless archetype is not going to be likeable, whether they are a positive or a negative archetype. So how do you give your character a soul?

* What *does* your MC care about? You say "himself", but what does it mean? What is it that he enjoys? Does he have any interests? Hobbies?
* How does your MC feel about himself? How does he feel about the world? Disappointment? Anger? Frustration? Acceptance? How does he feel about more idealistic people?
* What are his wishes for the future? More of the same, or a change? What are his expectations for the future, and how do they correlate to his wishes?
* What are the things the character wouldn't stoop to? Does he accept others doing that thing, or is it a complete dealbreaker?
* Given an opportunity to do something good / something bad at no cost or very little cost to himself, would the character do it?
* Are there any actions taken or not taken that the character regrets? Any doubts regarding doing or not doing something in the future?

Get to know your character intimately - their internal conflicts, fears, aspirations, know them better than they know themselves. Then see how you can show those facets of him in your writing.
Galastel had a fantastic answer. 

Make them likeable by making them human, "giving them a soul." No person, no matter how unlikeable, is grumpy and hates everything. (Example, Dolores Umbridge, from the Harry Potter series. She sucks! Most people hate her. But she'd likely show a soft spot for a kitten or something. A love of animals (cats specifically) is a relatable quality.) There are things that your MC will get upset/emotional about, or things that make them smile or make them more relatable as a person, or at least more realistic. 

This can all be done through subtle details (what draws your MC's attention? how do these things make them feel?) Your character doesn't have to be universally beloved, but if MC has absolutely no likeable qualities, consider developing them further before moving on with your story.