Shia Muslims mourn the tragedies of the Prophet (SAWA) and his Ahlul Bayt (AS) more than any other Muslim sect. No doubt, the tragedy of Imam Husain (AS) in Karbala is the greatest tragedy in the history of human kind looking at the details of it and the way it happened and the victims from infant child to women to the Imam himself and the inhuman acts by the enemies even by preventing Imam Husain and his family from drinking water despite being on the bank of the river, and other details of the tragedy which was declared by Imam Hasan before Karbala (No tragedy will be like your tragedy O Aba Abdillah (Husain)).
Our mourning on the tragedies of Imam Husain (AS) is according to greatness the deepest extent of the tragedies.
No other Muslim sect mourn the tragedies of the Prophet (SAWA) and his Progeny like the Shia Muslims.
Wassalam.