You'd need to manually position the mesh which can be easy or difficult depending on how complex it is, or how dynamic it is. I've spent many hours taking 'dramatic' models and turning them into T-pose, it can be a real pain in the bum.
Generally I do my very best to straighten out one side of it, left half for example, and make it as perfect as I possibly can. I then copy/duplicate the left half, flip it on the X-axis and merge it to the left. If there are features unique to a side (like, a mutated/larger arm) then this won't work, of course.
Generally I do my very best to straighten out one side of it, left half for example, and make it as perfect as I possibly can. I then copy/duplicate the left half, flip it on the X-axis and merge it to the left. If there are features unique to a side (like, a mutated/larger arm) then this won't work, of course.