Yang Yi
In the "Analysis of the Three Kingdoms", Yi Zhongtian commented that Zhuge Liang's last order of forcibly retreat and leave Wei Yan alone was contradicted to what he personally instructed Wei Yan, such contradiction indirectly lead to the tragedy Wei Yan and Yang Yi. Hence the forcibly retreat might be the idea of Yang Yi, not Zhuge Liang, may be Zhuge Liang died before devising any withdrawal plan and Yang Yi fabricated the order. There are no evidences for this theory, though. Another hypothesis is that Zhuge Liang's final order "leave Wei Yan alone" simply meant "ignore Wei Yan", did not mean "kill Wei Yan". Shu Han's main forces must withdraw to guard the rear area, and if Wei Yan could not be stopped then just let him be.