Amputation of the big toe at any level.
To support the 30% rating, medical records should show that the metatarsal head was removed along with the great toe. Operative reports, pathology notes, or post-surgical imaging such as X-rays that confirm the extent of the amputation are particularly useful here. A VA or private medical examination that documents exactly what bone and tissue were removed can help establish this. To support the 10% rating, the same types of records would show that the amputation involved the great toe without removing the metatarsal head. Statements from you about how the amputation affects your ability to walk, bear weight, or perform daily tasks can help give context, but the level of bone removal is the defining factor that separates the two ratings.
Conditions that are often caused or made worse by this one. If you have any of these, they may be claimable as secondary service connection.