Quite the incompetent planning all around, really. Then again, the whole plan is the result of said planner-deity saying 'ah, shit, I need a do-over.' A do-over which happened to involve genociding nearly all of everything. >_>
I do like the irony here. The story is supposed to be an example of the infallible omni-being's amazing miracle powers, but with a critical glance you realize that it's a massive demonstration of that being's epic fallibility.
No, the best part is that said deity decides to annihilate humanity because we were having sex with giants/angels and making human-giant/angel hybrids.
You think I'm fucking with you, but you're wrong.
The other interesting bit is it notes the deity can feel regret for its past actions; thus implying said deity exists in some sort of single-directional time-like substance. And it goes about correcting a mistake not by going back and fixing it at its source in the time-stream-like-substance, but by wiping it out by erasing it in the deity's present. Implying, among other things, that the deity is neither all powerful in our universe nor independent from a universe or universe-like substrate itself, since it exists in a time-like substance.
And the method of destruction is rather poor too; instead of simply magicking them out of existence, it goes about devising an overly-complicated, rube-goldberg like plan which involves magicking in huge quantities of water before magicking away said water afterwards.