Oligarch rhymes with:
aardvark, avmark, ballpark, baumstark, benchmark, bevmark, birthmark, bismarck, bismark, calmark, caremark, cellmark, chilmark, denmark, deutschemark, earmark, equimark, esmark, furmark, goldmark, hallmark, hashmark, hundertmark, landmark, lexmark, lindmark, lundmark, matriarch, meadowlark, monarch, newmark, oakmark, ozark, pathmark, patriarch, pockmark, postmark, raymark, sanmark, skylark, southmark, torchmark, trademark, transmark, triarc, vandemark, vandermark, watermark, westmarc, westmark