You completely misunderstood a question, you no longer have a valid answer to supply, yet your stupid mistake has to hang around for everyone to see FOREVER.
Here is an example of what I see, please excuse the quality of my redacting. See I only have 2,348 rep yet I can see somebody else's deleted answer.
A similar question was asked on Meta. The only feasible way to permanently delete it is to have it removed from the database. That cannot be done by regular users or mods here, but you could contact SE directly.
I'm not sure if they will delete (your) posts just because you ask. You have a better chance if it involves personal information violating your rights or those of someone you represent (for example under GDPR rules).
The reason this is not so easy is because you don't retain all rights to the content even if you're the poster.
Since IPS is still in beta, you only need 2k rep to see deleted posts. That's why you saw it.
I think ColleenV's advice (in her comments beneath the posted question) makes perfect sense. In effect, she suggests that you perform these steps:
Undelete the answer that you don't want to be visible to every person with sufficient reputation who happens to come across the relevant page.
Edit the old answer by replacing the original answer with a simple, polite explanation along the lines of, "I was unhappy with my original answer to this question, so I've decided to delete it."
Save the edited version of the answer.
Delete the answer.
By this means, you will shield your original answer from anyone who isn't morbidly curious about its previous wording—which is to say, 99% of all passers-by who would otherwise be able to see the original deleted answer.
The most disturbing thing to me about your situation is that (you report) "I did that once and the post was edit back and I got told off for 'sabotaging' my own post." I see no legitimate reason for a moderator or high-reputation site user to make that criticism. Deletion isn't an act of sabotage—it's simply a matter of removing an answer from the discussion associated with a particular question. And editing away an embarrassing answer before deleting it isn't an act of sabotage either—it's just a way to put maximum distance between an ill-conceived answer and prying eyes.
It seems to me that if you want to bury something you previously wrote, you ought to be able to do so, to the extent described above, without being labeled a saboteur.
