Explanation:

- The word "debacle" implies a disastrous failure or breakdown. After such an event, negative emotions can often arise.

- Option 1: Revenge - Revenge indicates a desire for vengeance. While possible, it specifically relates to a retaliatory action, not necessarily the immediate emotional aftermath.

- Option 2: Bitterness - Bitterness is a feeling of resentment and animosity. It fits well with interpersonal conflicts following a debacle.

- Option 3: Amity - Amity means friendship and peace. It conflicts with the context of a debacle, which is negative.

- Option 4: Doubt - Doubt relates to uncertainty. It's less likely to describe the emotional tension between two families after a major conflict.

The most appropriate word is bitterness.