To go out with a bang means something comes to an end successfully or impressively.
The festival went out with a bang when the world-famous rock band came on to play.
John got a karaoke machine for his leaving party to ensure that he went out with a bang!
The fireworks at the closing ceremony ensured that the London 2012 Olympic Games went out with a bang.
Don't confuse it with
If you bang something out, you do something very quickly and in a rushed manner.
I had to bang out my last assignment overnight as I'd completely forgotten about it.
The London 2012 Olympic Games went out with a bang with a spectacular closing ceremony, featuring iconic British pop groups, supermodels and the winning athletes. During the ceremony, the flame at the Olympic stadium was extinguished and the Olympic flag was officially handed over to Rio de Janeiro, which will host the games in 2016.