God Kill the Mon was godawful. It's not the resolution (breaking point/character development is all fine, not that ti seemed to count for much in the end)- it's the utterly insane and ridiculous plot, from the 'moon is an egg' thing to the ridiculous 'poll the Earth' (or half the Earth) (that has electricity) (and also ignore it)- just far too far divorced from any sort of possible grounding, even for Doctor Who. The absolute worse of lazy, nonsensical science, totally unresolved plot points and unbelievable actions. It's also trumped in every way by Waters of Mars.
It's got pretty well trashed, though it has now been trumped by Forest of the Night which is now a candidate for worst new Who episode ever. Fan backlash on that one is massive, so KTM has become forgotten. It's brought back memories of the equally dire Fear Her, with which it has several similarities- irony here is that last week's Flatline, which was good, was in many ways Fear Her done well.