top 1 - "ya mat' tvoyu ebal" "я мать твою ебал" / "ya tvoey mamy rot ebal" "я твоей мамы рот ебал" = "I fucked your mom" / "I fucked your mother in her mouth"
also known as the most default curse sentence in the dota/counter strike community
top 2 - "ty pidaras ebaniy" "ты пидарас ебаный" = "you're a fucking faggot"
top 3 - "ty churka ebanaya" "ты чурка ебаная" = "you're a fucking (derogatory ultranationalistic term about people from the Caucasus region)
most insults come down to mentioning parents, homophobic slurs, mentioning ethnic minorities etc, the usual
you can look up the pronunciation word by word at https://youglish.com/russian
be noted that all these will likely lead to a severe head injury if you were to say that in front of someone publicly, I don't advise doing so