Like yourself, I don't frequent them for news often but their coverage of Trump (who I am not a supporter or fan of) was particularly egregious. When they lied about him, they just empowered his base to reject any criticism lobbied against him, regardless of how legitimate those claims were.
Two lies that come to mind instantly are the narratives that he labelled all Mexicans criminals and rapists, when he was pointing out crimes that some illegal aliens were committing.
https://www.cnn.com/2018/04/06/politics/trump-mexico-rapists/index.html
https://www.cnn.com/videos/tv/2015/...didate-donald-trump-immigration-intv-erin.cnn
https://www.nbcnews.com/think/opini...apist-trope-old-racist-colonialism-ncna863451
I believe PolitiFact has already debunked this from when Tim Kaine made the claim in one of his speeches.
Another one I found particularly slimy was the claim that Trump mocked a reporter's disability. This would have been believable had Trump not used the exact same gesture to mock Ted Cruz, who by all accounts is not physically disabled, during the GOP debates. It was a gesture he used to mock those who are easily flustered under pressure, not an impression of someone with a physical disability, yet I still hear it brought up as if it's fact.