
Richard in season five
(Season 6. Sorry, I accidentally put 5 in the title.)
I will forever hold the opinion that Meredith was 100% wrong in this storyline. She knew that Richard was drinking, she knew that he was operating impaired, and she didn't want Derek to tell the board because she didn't want to lose access to the special teaching and access to the special surgeries (that she wasn't really ready for) that Richard was letting her in on.
And when Derek wanted to go to the board and report him, she had the nerve to call Post It - to invoke their marriage vows and imply that she would never trust him as her husband again if he reported Richard.
I know a lot of people say that Derek did it because he wanted Richard's job, but the board had already offered it to him. Instead of automatically accepting, he went and warned Richard about it.