I figured Cut the Knot could use a companion card, and it's been a while since we saw Annihilate. It could use an update.

This doesn't seem like too much of an upgrade. It also doesn't feel at all green.

Getting rid of 'non-black' doesn't feel like an upgrade? That would be the main reason why I don't play Annihilate...

I can't comment on the 'doesn't feel green part', though, except it helps justify in my head why this card can target black creatures. I know, though... Murder didn't need another color to justify it, though. I don't know. Let's see what other people think.

GB feels right flavourwise to me, but I'm not sure why. Certainly any colour with black can destroy creatures. But mechanics-wise, I think G and U are the least creature-destroying colours.

This would look more natural in red-black or blue-black than green-black, to me.

Green doesn't feel on creature destruction when it's not obviously contributing something else, like on Putrefy. It just feels wrong to me. This could be pretty much any combination other than and it would feel more right.

I get the impression that it's probably not going to make the cut at this rate, anyway. If there's an opening in RB, WB or UB, though, I'd put this forward as an option.