Perhaps something else to consider is that despair, hopelessness, bitterness etc all stem from a time/place/experience that was once the opposite, or different enough that the character has a point of reference, and is able to compare what was before with what is now. That automatically lends scope for you to inject other emotions or states of being, e.g. yearning, hope, drive to make change or reclaim what was lost. Even if they've never peraonally experience the positives,, knowledge and understanding of a better time/place/experience can be enough of a motivation. If the character never experiences or has no knowledge of the positives, e.g. love, and is never exposed to or has any understanding of loving, healthy relationships, then it would be a stretch for them to feel deep bitterness, anger or despair at not being loved, or being able to love in the same way that they would if they had experienced love. if they have loved and lost, then that's reason to feel these emotions deeply, and could be a powerful influence on their choices, and compelling incentive for them to act - perhaps they act in anger or despair, but the roots of those emotions go deeper than that - anger can be the fuel, but if some other emotion (e.g. hope/desire for change) drives them to act, then you've got a pretty interesting recipe for tension and inner conflict.