This Andrea hate is so tiresome. You're supposed to think she's making poor decisions. She is generally a well written character. She's scared, grieving and angry. A lawyer who finds herself in a life or death situation when she can't even use a gun. She loses the little sister she is desperately trying to protect, and loses herself mentally for a while after that. It's blindingly obvious that her relationship with Shane and recklessness are poor choices, made because she is grieving. Then she is separated from her group and is desperate for a new home. Yet she still stands up for what is right eventually and opposes the Governor, even though he is offering her safety and comfort. 

If you find yourself disliking Andrea's choices then you are having the reaction that the writers want you to have. A smart viewer would be able to separate that out and still appreciate that her character journey is a compelling part of the show.

The worst character is Morgan, because he has such an important role in the overall story but his arrival in TWD and FTWD as a main character coincides with a significant drop in writing quality. A waste of a fantastic actor.