Lets see London has had numerous plagues the last of which was punctuated by the Great Fire of London.

It's been partially flooded many times over the years.

There was the Great stink (not a disaster I know but bloody unpleasant nonetheless) until Basiljet came along and sorted out the sewerage.

The Luftwaffe had a good go a flattening London from above during the Second World War and the IRA had a go as well from the late 70s through to the early 90s.

Last, but no least though, some good old home grown radicalised Islamic terrorists had a crack at it twice (only one of which was successful thankfully)

That covers most of it I think

(I have chosen to not mention the numerous invasions London has faced since its inception as there are far too many to mention but you get the point)