If your Ishta Devta is Krishna, then the following mantra is for you:
Krishnaaya Vaasudevaaya Haraye Paramaatmane
Pranatah Klesha naashaaya Govindaaya namo namaha
Which means:
O Krishna! Son of Vaasudeva, You are the Supreme Lord, remover of miseries.
You destroy all evil, O Govinda!
I repeatedly bow to You!