Gertrude is one of the most complex characters in Hamlet. As Hamlet's mother, Gertrude is discussed frequently in Hamlet. However, her lines do not necessarily piece together a solid characterization. She is often in the background of many scenes, although even an absence of presence can say something about her character. Since Gertrude is not particularly vocal, a person studying Hamlet must rely on what others say about Gertrude.
First, she is a powerful character. Described as "th'imperial jointress," Gertrude is one of the leaders of Denmark. Hamlet thinks Gertrude is particularly weak, despite her power, but this may say more about Hamlet's childlike angst than Gertrude's actual character. If the audience member or reader is to believe Hamlet, then Gertrude is a fickle character. She is allied with different lovers each day and she is consistently changing her word. Her love and politics are always mixed, and it is not clear (at least within the text) if she knows that Claudius is a criminal. If she knows that Claudius is a criminal, then she is an unsympathetic character. However, if she is manipulated by Claudius, then she is a more sympathetic character. Her grief could possibly explain her fickle nature during the course of the play.
It is difficult to make firm conclusions about Gertrude, which is one of the exciting things about her character. However, there are definitely certain characteristics that can be agreed on, such as her shadowy nature and fickleness.