who was most at fault

I feel that Tybalt is at fault for most of the down fall of Romeo and Juliet lives.  He is at fault for a couple of reasons.  This is because he killed Mercutio and wanted to kill Romeo.  The story says "Tybalt under Romeo's arm stabs Mercutio".  This is saying that Tybalt killed Mercutio while Mercutio was under Romeos arm.  This makes Tybalt at fault because it drove Romeo to go insane and kill Tybalt which ended up being where the downfall of the relationship comes to full effect.  Romeo then goes on to say "Either thou, or I, or both, must go with him." to Tyablt before he killed him.  This shows that when Tybalt killed Mercutio it drove Romeo crazy with rage and revenge and made him kill Tybalt.  This is then were the real downfall of the story starts because Romeo was banished which made Juliet crazy.  In the end these Tybalt is the main reason for the downfall of Romeo and Juliet's relationship.