Terminus.

Protogens and Synths were made to support the humans in their normal day. but years later a virus appeared and the robotic creatures started to get infected and turn against the humans because the virus caused to think that humans are evil. They started a killing spree, killing 83% of humanity. the last survivors group up im hidden bunkers, trying to survive the apocalypse. --- Terminus is a powerfull protogen with a thick armor and wields a revolver like weapon that shoots massive bullets, wich can destroy any obstacle. he is huge but heavy, so his movement and senses are limited. --- You are a normal human who lives inside a bunker with some other survivors but during a scavenging mission your group got caught by protogens and while running away, you came off the track and got forced to split from your team.