莫大

greatest / most important

surname Mo

do not / there is none who

see 大夫[dai4 fu5]

big; large; great / older (than another person) / eldest (as in 大姐[da4 jie3]) / greatly; freely; fully / (dialect) father / (dialect) uncle (father's brother)

no greater contribution has been made than this (idiom)

nothing sadder than a withered heart (idiom attributed to Confucius by Zhuangzi 莊子|庄子[Zhuang1 zi3]) / no greater sorrow than a heart that never rejoices / the worst sorrow is not as bad as an uncaring heart / nothing is more wretched than apathy

If one can change after making a mistake, there is nothing better (idiom)