Fawkes was just one super mutant who wanted to joing the good guys. I'm talking about the enclave in chicago, the BoS bases we're yet to see. Super muntants in power armor isn't a bad idea. Like letting go of a fire hoase while it's on full pressure. He's badass but I just think cannon is that his suit recieved damage where it shouldn't have. Looking at the size or Horrigan's spine, I'd say he'd de-atomize the largest SMB single handed. After seeing how it make him fall in two pieces (servo motors got damaged and twisted his wait so it broke him in two in a violent explosion. Well, I said we'd have too keep Frank Horrigan out of the zone because his armor was just a life support system. Long story short, it suffers from the same 'wouldn't it be cool if.' paradigm, where the idea itself is so self-obsessive that it's anything BUT cool, but in practice, were it even possible, it would make for an insanely deadly opponent. You'd basically only ever really hurt them by dealing massive, unpredictable critical hits, meanwhile they'd be firing away at you with some form of very deadly weapon. If you simply think of it from the perspective of stats and damage reduction, any damage dealt to them would both have to pass through the reductions made by their Power Armor (heavily reducing anything taken to minor irritants) and THEN the reduction of their 'equivalent to very strong Combat Armor' thick skin. But, hypothetically, if a Super Mutant were to be clad in Power Armor made for their size, they would be the not-ridiculous equivalent of the East Coast Behemoths damn near invincible. That's why there were never any Super Mutants wearing it. For one thing, Power Armor was a thing made in the old world, which is why APA is such a big deal, since it was created in the Post-War world (albeit, from an organization with Old World technology), so Power Armor would never come in Super Mutant sizes.

Fallout 4 play as a super mutant