A negative SPID (-2) is because of an orphaned distributed transaction.
Please follow below steps to kill it:
Step 1: -- Find the UOW Number
where req_spid = [SPID Number. It is -2 here]
Step 2: -- Copy the UOW number from Step one
KILL ‘[UOW Number you found for Step 1]’
This will kill SPID -2 (Negative SPID). For a more detailed discussion on this issue, please visit http://blog.consultdba.com/2009/12/how-come-i-see-negative-spid-and-i-can.html#links