A quote which really defines Lady Macbeth and Macbeth's ambition regarding power is "Power does not corrupt men; fools; however, if they get into a position of power, corrupt power" George Bernard Shaw. Lady Macbeth is more ambitious in terms of gaining power then Macbeth is and that Lady Macbeth will do almost anything to gain power, even evil things that she normally wouldn't do. This is shown when Macbeth and Lady Macbeth learn about the witches' predictions, then roles in the plans to murder king Duncan in order to gain power and then finally after the murder, Macbeth doesn't want to finish the plan making Lady Macbeth angry and causing a chance they might get caught and gain no power at all.
Lady Macbeth shows more ambition then Macbeth does in terms of gaining power regarding kingship. When Macbeth finds out about the witches' predictions and the first two coming true "Glamis, and thane of Cawdor: The greatest is behind" (1.3.124-125) meaning that he got a taste of power, making him thane of Glamis and thane of Cawdor making him more ambitious for the power to become king. Proving that he will do anything for power he decides that he is going to murder Duncan. When Lady Macbeth receives the letter from Macbeth learning about the witches' predictions and that two of them came true already, she becomes very ambitious towards gaining power. She doesn't believe that Macbeth will murder Duncan, so she makes a plan for the murder.
Secondly Lady Macbeth shows more ambition then Macbeth does in terms of gaining power regarding kingship. When Macbeth does not want to murder Duncan anymore, for he recognizes that he is a kind man, good king and thinks Duncan should remain the king. Lady Macbeth however shows more ambition for power, becomes very upset upon learning how Macbeth feels how he doesn't want to kill King Duncan anymore, she says "And Live a coward in thine own esteem" (1.7.46) meaning she's calling him a coward for