Make the Mexican Wave
Pyth, 12 bytes

V+Gt_GXGNrN1


Demonstration.

In Pyth, G is the lowercase alphabet. +Gt_G is abcdefghijklmnopqrstuvwxyzyxwvutsrqponmlkjihgfedcba, the character that needs to be uppercased in each row.

V sets up a for loop over this string, with N as the loop variable.

In the body, XGNrN1 is a string translation function. X translates G, the alphabet, replacing N with rN1, the uppercase version of N. r ... 1 is the uppercase function. This gives the desired output.