I've been playing a lot of Overwatch as of late and adore the art style, so I thought I'd use some of my downtime between projects to sharpen my Unreal 4 skills.
The main technique to achieve the style is to use an instanced Master Material with a high roughness and low specular value that I can interchange textures with.
The textures themselves are all done from scratch in Photoshop using photo reference to colour-pick from.
Lastly, the entire scene is dynamically lit using Light Propogation Volumes (To get the feature enabled, put "r.LightPropagationVolume = 1" into ConsoleVariables.ini and (re)start the engine) to achieve the realtime global illumination.
Music: PICE - Epilogue (https://8bitpice.bandcamp.com/album/insert-coin)