In extreme situations, it suggests a total absence of empathy or a total incapacity to put oneself's in another's shoes. It's a refusal to understand the other's position or argument. The emotions are so high they prevent any kind of listening.
Opposition energies never completely blend, but it does not mean they can't work together. Think about dancing in couples, it can be very harmonious. It is about finding middle-ground and compromises to restore harmony. Oppositions reveal differences through contrast. They can trigger debates. They also remind us we are distinct from others and that we have to learn to accept differences.
In birth charts or synastry, oppositions can suggest an incapacity to solve some personal issues and a hope that someone else will take care of these (a savior), while in reality, we should take our responsibilities for these and own them. Some manipulators can jump in and take advantage of these situations. Sometimes, it is just a matter of learning how to deal with our issues, rather than a lack of will to resolve them. External intervention and support can help.
Oppositions can also suggest refusing to face reality as it is. It is about wishful thinking and illusions. Although we may try to escape it, reality always wins in the end. In this respect, oppositions want us to open our eyes and to become mature. It points toward make or break situations and split roads. Should I stay or should I go? Which way to go? It is your responsibility to make a choice.
Oppositions can trigger perpetual motions. Once we overcome our imbalances, we reach a new level of inner peace with ourselves and in our relationships.
Other major aspects: conjunction, sextile, square and trine