In the release trailer for an upcoming game called Lawbreakers
The guys behind Tested were hired to build the armor used in the shot, which blends a bit of CGI and real footage in the trailer. In the above video, the builders go through the steps used to create the armor out of foam.
Using foam is a long-used material for costuming: it’s easy to cut and mold into the right shapes, and it’s easy to use to craft complicated and detailed shapes, like what you’ll find on power armor.
Here’s the original trailer: