The Meaning of Life, the Universe, and Everything.
I made a repeating command block that teleports you up 20 blocks every tick by accident. It was supposed to teleport you up 20 blocks once you went over it, but I forgot to add the distance parameter (execute if entity @a[x=_,y=_,z=_] run execute as @p run tp @p ~ ~20 ~ ~180 ~). I can't get rid of it with disabling command blocks (it's a singleplayer world), nor MCEdit (it doesn't support 1.16), it teleports you every tick and I don't know the exact location of it, so breaking it is almost impossible. Is there any other way of getting rid of it besides deleting the world, I spent ~half a year making it and it would suck to have to start over.