Attraction is tricky... I think what it looks like depends on how balanced the people are. You mentioned empaths. Let's use that as an example. There are empaths who are constantly overwhelmed by the feelings of others. They shift out of their own energy to match what others or feeling or to fill the voids they naturally feel within others. They are fixers and give until they are empty. They feel better when they think they can fix others, but we cannot really fix others and instead they drain whoever they project this broken person perspective onto. This is passive approach to empathy and this kind of state might attract the narcissist you mentioned. The narcissist then takes and takes, but what they take is lost because it goes into a bottomless pit. The combination of the two together is a net negative result and energy is wasted.

There is another kind of empath. There are ones who are able to connect completely with the feelings of others without being swayed out of their own preferred state of being. They generate their own desired feelings while simultaneously connecting to others. They give freely, but not to their own detriment. They simply generate what they are and allow others to take it if they wish. They aren't trying to fix anything. They are simply accepting and compassionate of others. A narcissist might be confused by this person because they sense the free state of giving of this empath, but they also sense a strength and boundary. The narcissist will typically walk away from this type of empath as they cannot get what they want. This empath will also walk away from a narcissist because they will not allow them to continue to feed off of them endlessly.

You mentioned unresolved trauma. It plays a huge role in my opinion. When we have holes, the holes seek a way to be filled. Hence the attraction. We often fill them in unhealthy ways when we are unbalanced. However, there is another type of attraction.

People who have fewer holes to fill and are in balance also attract their opposite, but it is a complimentary opposite. So in the case of the empath who is balanced they might attract someone who is emotionally open and gifted in another area they lack like perhaps some kind of other form of intelligence. So maybe an empath with a talented designer or leader. The two of them together create a net positive result as they collectively approach the creation of their future giving and taking reciprocally for the greater good of the team. They help each other to bring awareness to their flaws and they offer patches to each other while they grow in the places they have weaknesses.

I hope that helps a little. Its just my take on what I've observed between relationships that seem to look like two vampires draining each other vs. two stars dancing with each other.