Cerbera odollam

Between 1989 and 1999, more than 500 cases of fatal cerberus poisoning were reported in the southwestern state of Kerala, India.

An excerpt from the article 15 facts about Cerbera odollam
A lethal dose of the poison is contained in one kernel of the fruit and causes death within 1-2 days. Typical symptoms of poisoning include burning mouth, violent vomiting, irregular breathing, headache, irregular pulse, coma, and eventual death.