Building Booper

Now the heroes who raided our hideout are as good as dead!Building Booper was a Demon-level Mysterious Being and a member of the Monster Association.

Monster Association Arc
Building Booper is seen in Z-City blocking the heroes' escape and supply routes on the surface by making several buildings around the routes collapse. He is presumably died when the combined of Saitama, Waganma, Child Emperor and Underdog Man pushs the manhole below the two collapsed buildings, where he is standing in, sending the two collapsed buildings flying in the air, thus also sending Building Booper flying in the process and eventually falling to the ground which seems to result in his death.

Abilities and Powers
As a Demon-level Mysterious Being, it can be assumed that Building Booper was a fairly powerful monster. He had the ability to cause buildings collapse.

Trivia

 * Building Booper is a new Mysterious Being introduced when Chapter 111 was revised. Before the chapter was redrawn, Building Booper didn't exist.