Overpopulated rhymes with:
deregulated, deregulated, vacillated, violated, deregulated, modulated, vacillated, violated, coordinated, cremated, deregulated, dislocated, hallucinated, insinuated, modulated, negated, relocated, uncoordinated, uncorroborated, vaccinated, vacillated, vindicated, violated
Overpopulated sounds like:
overbilled, overbuilt, overfelt, overfield, overflowed, overplayed, overpopulate, overvalued