I kinda had Gren tagged as Bastion actually. While Gren is more cyborg like Genji, Gren has the backstory as a mere mook of an evil army who at some point stopped fighting for said evil army, and now tries to live a life of peace (For a war machine anyways). But situations occur where his talents for rampant point-and-click murder must reemerge, and is rightfully feared by all for having super cheap power even though just about anyone with half a brain and a bit of skill could counter most of his strengths. 

But yeah, we be Overwatch now. [@Guess Who] I highly recommend losing most of your limbs at some point so Grane could bring Robert's soon-to-be corpse to Gren where they can rebuild him. Better, stronger, faster. They have the technology. Then Robert can learn about Gren and Grane's affiliation with the White Fang, what Gren did to become who he is today, and perhaps a way they could all improve themselves.

You know, assuming this day ever ends and Team RGRT comes back from their mission.