Leona Lewis - Happy
It killed her career especially in US, and it also underperformed outside US compared to her debut era. Echo also underperformed. She should've picked I Got You or Outta My Head imo. Will she make it with her 3rd album?
Miley Cyrus - Can't Be Tamed
It was a top 10 hit and dropped fast, fans weren't ready with Britney wannabe-Miley, with more mature and sexy style. They prefered innocent-Miley. The album underperformed and her fame dropped quickly.
Whitney Houston - Whatchulookinat
This single became her biggest flop in years, followed by an underperformed album, Just Whitney. Although the final album, I Look To You did quite great and had Million Dollar Bill which was a hit outside US, but she failed to create a comeback like her heyday in 80s/90s and failed to have any significance hits in US.
Janet Jackson - Just A Little While
Although probably it was mainly because of The Superbowl incident, i think the single wasn't strong enough. It became one of her lowest charting hits. She never recovered after All For You era, although Feedback was a moderate mini comeback hit. I still expect a comeback from her though.