Krishna was cursed by Queen Gandhari, which led to his death and the destruction of his dynasty.

The Kurukshetra war left all 100 of Gandhari's sons dead. When Krishna approached her to pay his condolences, the grieving mother spitefully cursed him that he along with the Yadu dynasty would perish in 36 years. Krishna already felt that the Yadavas were already transforming into a morally decadent race and should perish and so he calmly said "Tathastu" (So be it) at the end of her declaration.