AHC: Have one of the "Five Dynasties" reunify China

Easy. Zhou.
Guo Rong had had 5 years reign of victories when he fell ill and died age 37, leaving a 5 year old son... soon usurped by Zhao Kuangyin, who was 33, and lived to be 49.

Butterfly away Guo Rong´s illness, and he unites China, while Zhao Kuangyin stays just a loyal official to him and to his heir wen he eventually inherits as an adult.
 
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