Please help me fix my partition table - I completely messed it up I messed this whole thing up in the course of manually removing a boot camp install. I then removed OSX while in recovery mode (yeah...). Disk Utility will not allow me to recover 750gb of free space. The Disk Utility GUI--whether in OSX or in recovery mode--will not allow me to delete the free space it sees. 

I reinstalled OSX through internet recovery, but it is stuck on a 248gb partition. I believe that is disk0s2 in the below:

When I open terminal and run

diskutil list


this is what I see:

    /dev/disk0 (internal):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                         1.0 TB     disk0
   1:                        EFI EFI                     314.6 MB   disk0s1
   2:                 Apple_APFS Container disk1         248.0 GB   disk0s2

/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +248.0 GB   disk1
                                 Physical Store disk0s2
   1:                APFS Volume Untitled                11.4 GB    disk1s1
   2:                APFS Volume Preboot                 45.6 MB    disk1s2
   3:                APFS Volume Recovery                1.0 GB     disk1s3
   4:                APFS Volume VM                      1.1 GB     disk1s4


I'm having a terrible time finding a command to nuke the whole thing and start over. I'd really appreciate the help recovering all my missing free space.

Also, FWIW, I have no idea what /dev/disk1(synthesized) is, but maybe it's left over from my boot camp, in which case I'd like to get all of that free space back too. There's no need to preserve data.

thanks all!
Boot to internet recovery.
Open the Terminal application.
Enter the following command.

diskutil erasedisk apfs "Macintosh HD" gpt disk0

Quit the Terminal application.
Install macOS.


FYI:

The synthesized drive disk1 is just the physical partition disk0s2 which resides on your 1 TB physical drive (disk0). This disk0s2 partition contains the volumes disk1s1, disk1s2, disk1s3 and disk1s4.