Complex sentence: In terms of staff casualties, the attack is the second worst in the history of the United Nations, the deadliest being the 2003 Canal Hotel bombing, which targeted the UN headquaters in Baghdad, Iraq.
Split into simpler sentences: In terms of staff casualties, the attack is the second worst in the history of the United Nations. The deadliest being the 2003 Canal Hotel bombing, which targeted the UN headquaters in Baghdad, Iraq.