The false accusations sullied his clean reputation built over many years.

sullied 是动词 sully 的过去式形式。sully 的意思是"玷污、弄脏"，常用于比喻意义上指"败坏(名声)"。这个词来自古法语 souiller（弄脏），与 soil（土壤、弄脏）同源。