I dont really like telling what i use, because when others use it, i see that as competition... Its kinda selfish, i know, but are you jsut wondering what technique i use? Or do you want to know so you can use it?
Its really nothing special, its a preset effect in the program i use.
I gotta say that the third one, the one of the Tower of Gods boss, was my favorite. The background blended in with the boss, and I'm a sucker for digital related things.