Who came up with the Berlin Wall?

Nikita Khrushchev

Answer

Krushchev was getting really mad at East Germany because so many of its citizens were defecting into West Berlin. He gave Walter Ulbricht, general secretary of the East German communist party, an ultimatum: you stop all these defections or I will.

Ulbricht called in his chief of construction troops, a real go-getter named Erich Honecker, and told him to design a barrier through which no one could ever escape then build it all the way around Berlin.

Honecker decided to build two six-meter-high walls with a field of landmines between them.

So...the answer is "Erich Honecker."