How to delete HN account completely?

As far as I know you can't just delete your account completely, deleting all your comments would be unfair, since the whole discussion would likely break apart.

But you can try to send an email either at info@ycombinator.com or pg@ycombinator.com and ask to make your account inactive, you could also change your email and delete any personal information.

Here are a few previous discussions that might give you, well, hundreds of comments which will answer your question.

https://news.ycombinator.com/item?id=10006616

https://news.ycombinator.com/item?id=9089177

https://news.ycombinator.com/item?id=2088545

https://news.ycombinator.com/item?id=1047101