Here’s a super condensed version: http://northstarfan.tumblr.com/post/110529621651/iandsharman-simptasia-piotr-rasputin

Northstarfan’s has a whole tag devoted to Piotr’s shenanigans: http://northstarfan.tumblr.com/tagged/this-is-also-a-colossus-hate-blog

Short answer – He has a history of being kind of an abusive dick who somehow got painted as a gentle giant.