Avandia is a very well known case. Media portrays it as if underhanded executives in GSK overlooked possible risks during its development.
But in reality similar risks are inherent in most of drug development, and there simply won't be any new drugs on the market if ALL risks were required to be zero. The additional risk of avandia is significant, but not really that great compared to risks of alternative medications (they are really not good enough), that's why the FDA let it remain on the market.
If you follow the drug industry then there are much more hilarious stories. Like finding out that your drug actually makes things worse for patients after the Phase II of clinical trials (at first company executives thought that the control group and the treatment group were mixed up).