Does The Guardian do any investigative reporting? Like the Washington Post at least used to do, and I think the New York Times still does.
They revealed the existence of PRISM and afterwards published lots of analysis on the Snowden leaks. I believe they were also involved in the Panama Papers and I believe they broke the news about a UK/US black site and some war crimes after the invasion of Iraq
And Spy Cops: https://www.theguardian.com/uk/2011/jan/09/undercover-office...
The BAe bribery scandal: https://www.theguardian.com/world/2003/sep/11/bae.freedomofi...
And before that the downfall of Jonathan Aitken and Neil Hamilton in the 1990s.
They have a search tag for it, although it's also used for articles about investigative journalism so you have to scroll a few pages.
If you just want examples, the articles about various journalism awards often list topics from that year.
If you combine it with the 'tone/news' tag, it narrows the field quite a bit:
https://www.theguardian.com/media/investigative-journalism+t...