The answer is Major burn.
Major burns are often a clear and immediate sign of abuse, especially in cases where the burn patterns are unusual or inconsistent with the explanation provided. Burns can result from scalding, contact with hot objects, or even chemical burns, and they are typically noticeable right away.
Renal failure is less likely to be an immediate sign of abuse. It can develop over time due to various factors, including chronic neglect, dehydration, or poisoning. However, it is not typically the first sign that would be noticed in a clinical setting.
Hypothermia can be a sign of abuse, particularly in cases of neglect or exposure to cold environments. However, it is less specific than major burns and can result from various non-abusive situations as well.
Laxative overuse is least likely to develop first among the listed options. It typically indicates a pattern of abuse or neglect over time, often associated with eating disorders or attempts to control weight. It is a more chronic condition and less likely to be the initial sign of abuse.