Bats invented the Red K, though, and Talia stole it from the Cave. It's synthetic, he was developing it for the sole purpose of taking Clark down.
The story's pretty clear on the fact that these are Bruce's plans, start to finish, which is a massive failing. Even apart from the lethality question, Clark's, Diana's and Arthur's are incredibly bad plans; they don't pass the "ask a ten-year-old" test. Give Arthur an hour to do all the damage he likes. Leave Diana's insanely powerful body with a big ol "no vacancy" sign over the door for any passing Deadman or Starro. Do SOMETHING to SUPERMAN but WHO KNOWS WHAT, because that can't possibly end up a disaster, no sir. I mean, Bats is a dick, I'm the first to say it, but the man is not stupid, and those plans were.