<Tr> <Td> </Td> <Td> Unification under Prithvi Narayan Shah </Td> <Td> 25 September 1768 </Td> </Tr> <Tr> <Td> </Td> <Td> Thapa dynasty (under Shah dynasty) </Td> <Td> 1806--1837 and 1843--1845 </Td> </Tr> <Tr> <Td> </Td> <Td> Rana dynasty (under Shah dynasty) </Td> <Td> 1846--1953 </Td> </Tr> <Tr> <Td> </Td> <Td> Constitutional monarchy </Td> <Td> 1990--2007 </Td> </Tr>

Who introduced abolition of slavery system in nepal