Timecop

Logan gets a new partner - Bruce Campbell! - in episode 9 of Timecop.

Logan goes back to World War 2 without killing Hitler but then someone goes back to 1989 to kill Logan in episodes five & six of Timecop.

Timecop decides it's all serialization all the time(cop) as Jack Logan squares off against his arbitrarily assigned arch nemesis in episodes three & four.

They're sending cops back in time to solve mysteries like 'who killed Jack the Ripper?' and 'where'd those diamonds go?' in episodes one & two of Timecop.