The step by step procedure to deactivate or delete your slideshare account:
First log in to your slideshare account
Then click on Account settings from the drop down menu
And then Click on the Change Password tab
Click on Delete Account which appears below(as shown in fig)
A confirmation message occurs to delete your account. Click on "yes, delete my account"
And in the next step you have to enter your password and reason behind your account deletion nothing but feedback
Finally you get a message of successful deactivation of your account