No, I'm looking at some of the larger pieces of background we are given: how the Monsters ultimately did not leave survivors beyond the one on Factor.
Speculation that is highly, highly unlikely based on the evidence we see.
There is never a point where diplomacy can morally be completely rejected as a possibility in favor of massacre when we are talking about bystanders and uninvolved parties.
In all probability the Monsters have been slaughtering and invading for awhile and being beaten back and killed for awhile: we have no reason to believe, based on any existing evidence, that they ever did otherwise.
And from Kala it seems apparent that they had Goliath, Kraken, and Wraith samples without an indicator that they had others, based on how her abilities are said to be tied to those three.
Sounds like the corps are willing to invade if the colony strikes one of the most valuable minerals around.
Neither she or anyone else would consider founding a colony if such a thing was the norm.
Honestly from Markov's lines I'd guess he just likes fighting and being a hero.
Not to say the corps are saints, only that they aren't hilariously evil like you posit.
So one colony being by some corp seized means they are all totally evil to you?
Hank and Markov both spoke to Val that they preferred the colonist life over the Hub life of less upward mobility.
Honestly I think the governments and corporations in Evolve are purposefully morally grey much of the time.
I grant that the Relays may be, and from hints probably are, doing something bad and that the Monsters may be justified in destroying them.
But as you say this does not justify their other unethical actions.
By that logic they would exterminate any intelligent race capable of Patterson tech, again with at best pathetic attempts at diplomacy.
The kind of massacre they are depicted as implementing earns a solid "proven evil until proven otherwise" from me.
And for what they do to not be evil would require a very convoluted conspiracy where every killed colonist was a collaborator in something deserving death.
I'm pretty sure word spread quickly that the Monsters were serious business, and in any case after a certain point it would be clear that fighting them is a death sentence for most.
I haven't quoted, but I have cited where my information comes from.
It would take awhile to track down the exact conversations I refer to in order to quote them accurately, I was hoping they were simply common knowledge.
You are taking a very literal interpretation of "everyone" from Slim, where elsewhere he says all his friends are dead.
Seems more like typical horrific war trauma than a total massacre.
I won't argue that Hub isn't evil in doing that: I don't think any of the big factions seen are ones I'd really root for beyond humanity in general.
The Hunters are obviously heroes, but they are a tiny group of brave crazy people, not a real faction.
As a last thought, Hub seems to be if anything the only non-corp government in the story bigger than a colony, aside possibly the Hegemony which was only briefly mentioned in the Basilisk Wars and which we have very little information on.