The sinking of which vessel in 1873 was the greatest disaster for the White Star Line prior to the loss of Titanic in April 1912?

The SS Atlantic

https://en.wikipedia.org/wiki/SS_Atlantic_(1870)

White Star Line had a couple of losses especially in the North Atlantic: RMS Tayleur in 1854, SS Atlantic in 1873, SS Naronic in 1893, RMS Republic 1909 and, of course, RMS Titanic in 1912.

Regarding the death toll, the loss of the SS Atlantic was the worst disaster prior to Titanic. At least 535 passengers and crew lost their lives.

The passenger list:
https://www.immigrantships.net/v6/1800v6/atlantic18730320_04.html