I personally love Brutalism, but some of its buildings I would not shed a tear if they were lost.
One example being One Yonge:
To me it isn't even a good
example of Brutalism.
Local examples of Brutalist buildings I would absolutely hate to see demolished:
Robarts Library (Fort Book) in Toronto:
222 Jarvis in Toronto:
University of Waterloo Math & Computers Building:
Keep in mind I'm only using local examples because those are some I know the best and have some attachment to, there are many more examples out there that would be a huge architectural loss if they were demolished (J. Edgar Hoover Building, Dallas/Boston City Hall, etc.).
We may think these are ugly now, but just like the crimes that occurred in the 60's and 70's, once they're gone, they're essentially gone forever.