We have a newly added report that gives you the dynamics of a resolved or completed ticket to track the changes made to it which include SLA violations, reassignments and the response time recorded on them. 

This is called "Ticket Lifecycle" which aids this in depth studying of the activity on each ticket that can be filtered using these parameters: time period, customer, source, priority, product, SLA violated, at least once in a group, at least once in agent and at least once in status.

Kindly note that this is available from the Estate/Pro plan and above. Documentation on this is given below: