Difficult Customer Situation Handler

Help me handle this difficult customer situation.

The situation:
- Customer type: [INDIVIDUAL/BUSINESS]
- Relationship history: [NEW/LONG-TERM/REPEAT]
- Revenue from this customer: [APPROXIMATE VALUE]
- The problem: [DESCRIBE WHAT HAPPENED]
- Customer's complaint: [WHAT THEY'RE SAYING]
- What's valid about their complaint: [HONEST ASSESSMENT]
- What's not accurate: [IF ANYTHING]
- What I've done so far: [ANY RESPONSE GIVEN]
- My desired outcome: [KEEP CLIENT/CUT LOSSES/REPAIR RELATIONSHIP]

Help me:
1. Understand the customer's perspective and emotion
2. Identify what went wrong and whose responsibility it is
3. Determine the appropriate level of remediation
4. Draft a response (email or talking points) that:
   - Acknowledges their experience
   - Takes appropriate responsibility
   - Offers a specific resolution
   - Sets boundaries if needed
   - Preserves the relationship if possible
5. Create a prevention plan so this doesn't recur
6. Decide if this customer is worth keeping (cost-benefit)

My policy for this situation: [IF I HAVE ONE]
My bottom line: [WHAT I WILL AND WON'T DO]