Which character is willing to decieve his friends for his own ambition?

The character whose willing to deceive his friends for his own ambition is none other than Cassius.

In William Shakespeare: Act 1 entitled the Tragedy of Julius Caesar, Gaius Cassius Longinus perceives the true motive of men and is also a great observer. Cassius does not resent the almost dictatorial pronouncement of his equal, Brutus. This Cassius is a long-time friend of the main character, Julius Caesar. But because of Caesar's ability to gain power, Cassius turned his back against Caesar for he was jealous enough not to have power unlike Caesar. He was the one to lead Brutus to kill Caesar, but over a period of time, he allows Brutus to take over and lead the conspiracy. 

To sum it up you’ll get in a lot of trouble and even some legal action can be taken