Most "frisson" with someone with whom I had a summer fling in my later 20s several years before meeting and marrying husband. It was all physical, though. The guy was otherwise not my type and I knew it. There was no desire to make it more meaningful than it was. No regrets about the fling, nor about its end. Just some nice (hot) memories.

The chemistry was strong with the other person because we did a lot of growing up with each other (post college). Each other's first serious, I love you relationship added to the electricity. It ended badly and we have had no contact in years, but at some level I believe we will never forget each other.

OP, haven't you asked this question a dozen times before? There is a poster who has been asking this question at least twice a month for the past few months..

If you're spouse or SO isn't the person that you've had the greatest chemistry with, who was? And, what made the chemistry so strong with them?