Regicide (noun). - English meaning: A person who kills a king/ the act killing of a king. - Bangla meaning: রাজহত্যা, রাজহত্যাকারী, রাজহত্যায় অংশগ্রহণকারী ব্যক্তি।
Other options, Genocide - The intentional killing of all the people of a nation, religion, or racial group. Patricide - The crime of killing your own father. Parricide - The crime of murdering a close relation, especially a parent.
Source: 1. Cambridge Dictionary. 2. Accessible Dictionary by Bangla Academy.