Deleting the file isnt enough.
Discussion
Please free to add any extra information that could be useful to the crowd!
A key that ever existed on a computer that is later connected to the internet isnt provably better than a hot wallet.
I agree!
One level up is to boot a live linux disto on a diskless offline PC with a bitcoin wallet included - like https://tails.net/ for example
but still not good enough, only a bit better