As a preliminary consideration, it is common misconception that one can scour their credit report, find any error/inaccuracy, and then get the entire account or all derogs removed based on a dispute of some inaccuracy.
A dispute is limited only to the verification, correction, or if neither of those can be done, the deletion of the specific information that is under dispute.
The furnisher can either verify the accuracy as reported, or correct their reporting, without any issue of deletion of the information.
Additionally, even if the information cannot be verified or corrected, deletion only applies to that information, and not to other reported information.
"Last activity" is not actually even a specific, reported item of information. Rather, it is reference by the CRA to the last date any activity occured.
It may or may not refer to an added, new, or inaccurate delinquency, and is not typically a specific reporting by the creditor that is subject to their investigation.
I would not dispute the accuracy of a date of last activity. It is not a reported item and usually has no effect on scoring.
It is the payment history profile itself that is subject to dispute, and such disputes can often lead to the creditor adding each an every possible monthly delinquency to you payment history profile.
