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This is typically done in Anime quite frequently. Usually anime has a whole slew of main characters that each have their own tropes... and usually 1 of them are dark/were dark/converted/converting...
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#2: Initial revision
This is typically done in Anime quite frequently. Usually anime has a whole slew of main characters that each have their own tropes... and usually 1 of them are dark/were dark/converted/converting. I don't see it being off putting. It's more so the trick of making the audience empathetic to their plight. Are they running away from their past to realize that everything they knew was a lie? Is their actions of "evil" (dark arts and being evil are in my opinion 2 separate things though they are usually taken as the same EX: See professor Snape from _Harry Potter_) due to their past and they do it out of fear/hate for the other? Often in anime, you will see a child of an evil lord who ran away from their dimension and hide on Earth. This person would typically be viewed as technically dark/evil and do things in their way because they don't know any other way. Then you have the other Main protagonist enter the scene and show them the truth and the light of the world and slowly this person converts/builds the bonds they were searching for and act in open rebellion against their parent's ways and usually give some cliche speech about friends and that not everyone is trying to hurt them. So Yes, it is very possible to have a protagonist be dark, live a dark current/past life and have them be liked by the audience. It is just a matter of how you portray them.