usurper

Etymology

From usurp + -er.

noun

1. One who usurps.
   The fact that the Yongle emperor was therefore a usurper, regicide and nepoticide (nephew-killer) made compiling the Veritable Record – or official history – of his reign a most dangerous scholarly post. The official given this ticklish task managed to survive several drafts, finally producing one that pleased his master as it omitted the dead nephew's reign altogether. 15 September 2014, Martin Gayford, “There's more to Ming than a vase [print version: 16 August 2014, pp. R6–R7]”, in The Daily Telegraph (Review)