I would rather say handle this Salesforce rather than in SFMC. If you are to do the lead scoring computation in SFMC, you would need to develop a SQL query based on your send and click object. AMPSCRIPT would not work as Open or Click activity are not generated during email send. Even if you are able to compute the lead score, you cannot use OTB functionality using Marketing cloud connect for transferring the lead score back to Salesforce.
Best option is that in the Salesforce, whenever you execute a send against a lead id, a record is created in Individual Email results object and the Individual Link details object through OTB Marketing cloud connect. Individual link detail object contains the details of the link opened/ clicked by a lead. These objects are related to Lead Object using Look up relationship. You can very well write a cross object formula field or a simple apex class in Salesforce to evaluate the lead score based on Link Clicked