Don't know about "cheating", but there's a match from 10 years ago I'm still mad about.
2009-10 season, away at Chelsea: blatant last man foul in the box by Terry on Rooney, nothing given. Then some dodgy decisions (offside? penalty not given? don't remember) against Valencia too.
Chelsea won 1-0 from a late free kick (some obstruction as it went in too I think), scored by Terry.
League decided by a point. (Same season as Drogba's very offside goal, but I think Macehda handled for his goal that game too).
Luiz's debut game (2-1 loss at the Bridge) was worse refereeing, he should have got a red and 2 yellows for various assaults and dives, but don't care since the league was won.
On the other hand, referee also let this slide in that game:
e - you can enjoy more salt i found the match day thread
https://www.redcafe.net/threads/chelsea-vs-manchester-united.274182/page-32