Based on the reviews it seems like it's had an ownership change and renos at some point, but when I was in Ottawa in the early 2000s this was the absolute worst building I ever went into:
https://goo.gl/maps/XjqZbBR9arz
Dow's Lake Towers. I was warned not to use the elevators as they usually jam, there was broken glass and garbage in most of the hallways and it smelled like rotting food inside. On two of the several times I was there (a friend from undergrad lived there) we had to vacate because of a fire alarm. His unit was absolutely disgusting as well, although he deserves some of the credit for that one.