Have a look at the following link
en.wikipedia.org/wiki/List_of_trading_losses
There are 45 instances listed, of which 19 for over $1bn;
Most of the losses were brought by a lone trader; UBS has the privilege of appearing twice on the list (Ramy Goldstein for 430 M$ in 1998, Kweku Adoboli for 2 bn$ in 2011)
en.wikipedia.org/wiki/List_of_trading_losses
There are 45 instances listed, of which 19 for over $1bn;
Most of the losses were brought by a lone trader; UBS has the privilege of appearing twice on the list (Ramy Goldstein for 430 M$ in 1998, Kweku Adoboli for 2 bn$ in 2011)