##Actually, 13 bytes
Actually, 13 bytes
5Pτú;∙♂M╪k♂Σi
-4 bytes from Leaky Nun, and the inspiration for 4 more, then 4 more from him, and 1 more from me
Explanation:
5Pτú;∙♂M╪k♂Σi
5Pτ push 26
ú;∙ Cartesian product of lowercase alphabet with itself
♂M maximum of each pair
╪k list of length-26 sublists
♂Σ concatenate each sublist
i flatten and implicitly print