Compute a complex power
Jelly, 8 11 bytes

Thanks Johnathan Allan for updating the answer with the rules change.

ı_*@µĊ,ḞAÞṪ


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ı_*@        z^(i-z)
    µ       new monadic link
     Ċ,Ḟ    pair real and imaginary parts
        AÞṪ sort by absolute value and take last value