Don’t be such an idiot, of course you are capable of accidentally injuring or killing your kid. There are a thousand ways a small child can die, and while a good parent keeps them as safe as possible, there are no guarantees in life. The kid could dart out into traffic, fall down the stairs, be bitten by the family dog, hit their head on the slide at the playground, get abducted by a pedophilic neighbour, etc, etc, etc. One could argue that any of these things involve at least a little negligence on the part of the parent - but parents, being human, are not infallible.
Sure, these things will not happen to most parents, and most kids survive their childhoods unscathed. But it’s stupid to insist that nothing bad could ever happen to your kids, and that’s essentially what you are doing.
Besides, as you keep ignoring in the other thread, you have clearly admitted your ability to leave your own child in the car:
A lapse of a few seconds is all it really takes, despite the fact that you want to pretend it isn’t. If you can make this brief error, I don’t see what’s stopping you from making an error of a greater magnitude.