The YouTube Adpocalypse is a name coined in early 2017 to describe a site-wide withdraw of advertisers that affected the platform. After the initial controversy, several advertiser-connected controversies were also referred to as "Adpocalypse".
Some creators say that Adpocalypse started as early as August 2016 when YouTube started shifting their focus towards more "family-friendly" content. Many channels with adult viewers and more serious/spicy overtones noticed a difference in their earnings.
2017 and 2018
In February 2017, Youtuber PewDiePie came under fire for content that YouTube deemed "anti-Semitic" and "hate speech". A lot of major brands (Coca Cola, Disney, etc.) pulled their advertising as a result.
Later that year concerns regarding advertising on kids-oriented channels resulted in YouTube amending their Partner Program.
In 2018 Logan Paul posted a video from his trip to Japan, where he reacted to finding a body. This prompted a lot of backlash towards him, and resulted in YouTube updating their policies.
February 2019 - MattsWhatItIs
May 2019 Vox Adpocalypse (Adpocalypse 2.0)
Suzy Lu, drama channels possibly going after each others' sponsors.