Due to my extremely powerful senses of observation, I can tell this topic is about: who's stronger, NTF or Vasudans; would GTVA have won without Colossus; who's fault is it for the invasion; which is better, apple pie or ice cream.
Anyway, I'm gonna jump on topic 2, which seems like a no brainer to me: GTVA would certainly have won against the NTF without the Colossus. With the Colossus it helped, but the NTF was doomed either way. They had limited numbers and held only 3 systems, as opposed to the entire military force of two combined species that held all known systems except for the NTF's three and Sol system. In a strict sheer-numbers game, GTVA wins hands-down. Can't understand why that topic is such a debate...
As for who's responsible for the invasion...well, yes, Bosch opened the portal. That's certainly his fault. But the GTVA gained control of it and held it, and refused to shut it down in the effort to learn how to build one. So part of it is their fault too. I don't know how quickly they reacted when they spotted the Juggernaut in the nebula and tried to blow up the Knossos, but if it was a slow reaction it's even more their fault for not blowing it up earlier. Not sure that would have made a difference since the portal may have stabilized anyway...