What do you mean by the bottom left piece? I thought you were just trying to hang one sheet? Do you mean there is a high spot somewhere causing the corner to be floating out an inch from the framing? You are going to need to find the source of that high spot. 1" is just too much to work around I fear. The corner of the sheet next to it is going to be off, at least with the surface of the sheet you are trying to hang, etc. etc.
Hopefully you can source the problem to a stud or two and reposition them. Maybe you let one past you without checking to see if it was badly crowned or something? If this is the case you are going to have the opposite problem on the other side of the wall but fir strips might work to build the wall up to flush.
If you can isolate to one such crowned area you could plane or power plane it back to being flush---perhaps. Again, 1" is a chunk of space to find at one corner though. If inspectors I work with saw 1" taken off a framing member or two I doubt they would sign off. I think you need to plan on some framing adjustments.
Do you, by chance, have an electrical box you forgot to trim for? That could be pushing you out an inch.
Others will have better ideas I hope.