Which ruler of Magadha assumed the title of "Ekarat" or sole sovereign ?

Q. Which ruler of Magadha assumed the title of "Ekarat" or sole sovereign ?
Answer: Mahapadma Nanda
Notes: Mahapadma Nanda was the founder of Nanda dynasty. He overthrown and killed the last Shishunaga ruler Mahanandin. The puranas described him the "ekarat" meaning sole sovereign or "sarva kshtrarantaka" meaning destroyer of all the kshatriyas.