Answer: irate
Explanation: In simple words, irate refers to the complainers who share their negative opinion about an organisation within a small group. They usually complain so that others could benefit from their review.
In the given case, Tom is complaining about the lousy service from his friends but not to any third party. Also, he is doing so with the intention of awaring others.
Hence from the above we can conclude that Tom is an irate kind of complainer.