A pain reliver used form sever pain like post - operative pain or pain due to terminal cancer :

Explanation

To answer the question regarding a pain reliever used for severe pain such as post-operative pain or pain due to terminal cancer, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Type of Pain**:
- The question specifies severe pain associated with post-operative recovery and terminal cancer. This indicates a need for strong pain relief.

2. **Understand Analgesics**:
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