Hmmm....
When we love someone, we do wish for the best for them, while we may be apathetic or indifferent about those we don't love. But then we may wish the best for someone we feel compassion toward as well. We may wish evil on those we hate while being apathetic or indifferent to those we don't. I don't really see attachment as the opposite of love as much as something that is perhaps mistaken for love.
I tend to gravitate to fear as being the opposite of love.
Love does draw us closer to others, while fear tends to push us away.
Fear tends to create separation between us, while love tends to remove that separation. I don't think the opposite of fear is bravery as bravery seems to require fear as one if it's ingredients. But then again, it seems to me that we can fear someone we love as well....so....???
IDK, perhaps love does not have an opposite. All of the colors in the color wheel have an opposite, but white contains them all. White doesn't really have an opposite, black is just darkness, a lack of light. Perhaps love is a mix of all of those other emotions we feel when we are connected in one way or another to others. Then perhaps the opposite of love is indifference after all, no feelings at all, emotional separation. Of course toward one thing or one person this doesn't sound quite so awful, but what would it be like to have no love for, no connection to, anyone or anything at all? Perhaps separation is the opposite of love?