It depends on what's going on with you guys and how the relationship was. If it totally blindsides him like if you lead him to believ things were great by your actions and words than yeah he might do something to really hurt you(not physically). It also depends on how much he was "in" with you... we take it as betrayal, like "you have the audacity to break up with me" after all i've allowed myself to show you and indulge because most a lot of us feel like... we specifically picked you because we are very very picky about who we will have a relationship with.
He might tell you about yourself and all your negatives and make you feel like . I think It really all depends on how he feels about you and how he viewed the relationship.