Final answer:
The most likely complication for a client with diabetes receiving cosmetology services is delayed wound healing.
Step-by-step explanation:
The complication that is most likely to occur in a client with diabetes receiving cosmetology services is delayed wound healing. In diabetes, increased glucose concentration in the blood for a longer duration of time can lead to excessive growth of microorganisms, making the client more prone to infections. This delay in wound healing is due to the reduced ability of the skin to regenerate in the dermis layer, resulting in slower healing.