As someone who can speak somewhat decent Hindi here are some insults I use on scammers. Trying to phonetically spell them out with an american accent. Please add any if I missed stuff. Will add more to it as time passes. Here are some basic to advanced insults that you can use:
Basic:
Ben-chod: Sister fcker
Madar-chod: Mother fcker
Bho-sari: Pssy
Bho-sari-ka: implies your moms a whre
Luhnd: Dck
Cho-tea Luhnd: Small Dck
Gandu: dumb angry person
Kutta: btch
Medium:
Sharam hey yeah nah-hee: do you have shame or not.
A bee dar lag raha hey choo-tea-yea: feeling scared now fcker
Bol bimari chor: speak now you lower class thief.
Pay-lay hang-ray-zi seek-ho randi: first learn english you whre
Advanced:
A bay bho-sari ke soon beech ras tay pay kap day knee cal kay nah teri gaand main helicopter shot maroon gah: Famous cricket insult/meme in india.
Bat ka grip knee cal ke nah see that eri gand me dal: fun meme from the god of cricket.