Excessive intake of alcohol most commonly affects kidneys/liver.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the effects of excessive alcohol intake on the kidneys and liver, specifically which organ is most commonly affected.

2. **Identifying the Affected Organ**: Research and medical studies indicate that the liver is the organ most commonly affected by excessive alcohol consumption.

3. **Mechanism of Damage**: When a person consumes large amounts of alcohol, the liver has to work harder to metabolize and detoxify the alcohol. This increased workload can lead to liver damage.

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