Amazon's substantial investment in combating return fraud, including the use of machine learning and a large dedicated team, demonstrates a strong commitment to minimizing losses and improving customer trust. This proactive approach is likely to positively impact investor sentiment in the short term, as it showcases Amazon's capability to tackle operational challenges effectively.

Kohls Corp.'s adjustments to its return policies represent a direct response to the challenges of return fraud. While these changes aim to reduce fraudulent returns and associated costs, the impact on the stock is neutral in the short term. The effectiveness of these measures in reducing fraud without alienating customers will be key to assessing their long-term impact.

Walmart's mention of potential higher prices or store closures as a response to fraud highlights the significant impact of return fraud on its operations. However, specific strategies beyond this warning were not detailed, making the short-term impact on the stock neutral but noteworthy for investors monitoring retail sector challenges.