In couple counseling, we do see a lot of misunderstanding between 2 people, and although initially, they find the “opposing” characteristics attractive, over time, their mind focuses on the negatives of these traits. Part of couple counseling is to give these folks the emotional literacy to better understanding each other, and through that understanding, they can work towards accepting, acknowledging, appreciating, and reconnecting with each other again, rather than blaming each other for their differences.
The common observed differences in the couples that I see are....
1. One tends to be the “bigger picture” person, and the other more detailed focused.
2. One tends to be more introverted, and the other more extroverted.
3. One tends to be more emotionally detached and logical in decision making, and the other tends to be more fused and “feeling” orientated.
4. One tends to entertain big, dreamy goals, and the other one more orientated towards SMART realistic goals.
5. One tends to be more present and loves to go with the flow, and the other more past and future orientated.
6. One may be more focused on connection, stability and control, and the other more into newness, growth and novelty.
There are many more perhaps. You might like to add them here in the comments.
Of course, these can complement each other very well, and at the same time, can also create ongoing conflict if unaware.