[quote]Why is Spartan Locke trying to kill master chief?[/quote] He isn't trying to kill him specifically. He and blue team are AWOL and ONI and UNSC want them back [quote]Why is Spartan Locke in the beginning cutscene of halo 2?[/quote] It is him and Fireteam Osiris talking with The Arbiter about the Chief. The Arbiter then shows Locke the events of Halo 2(Unless I am wrong) to show him how He met the chief.