Cecil seems to be far better equipped both at fighting Viltrumites and finding their weaknesses I mean how is earth the only planet to figure out that they’re vulnerable to sonic weapons? Surely the rest of the galaxy would have found this out during the millenia of fighting the viltrumite empire? And earth has creatures like the Kaiju which when drugged up could probably kill at least an individual viltrumite if not a small group. I mean so far the best thing the WHOLE coalition of planets could come up with was Allen and he wasn’t even close (although from what I’m told he gets stronger) Is there anything else the coalition does it the comics maybe? Please correct me if so.
Another difference is earth is one of the few worlds that has super powers and is constantly fighting itself and making more weapons to kill more efficiently Soo couple with continually trying to kill each other off with superpowers beings who all do their own thing makes it a harder planet to conquer then your average world