When you get to Regret in the level Regret dodge the honor guards and charge for Regret. Press X on his chair and you will be riding his chair. Now? Beat some sense into him.
With hunters shoot them in the exposed neck with a sniper and they should die . I tried this on normal so im not sure about heroic and legendary mode.
According to GameDaily Biz, Bungie Studios' own Director of Cinematics, CJ Cowan, will be giving a special feature presentation at ADAPT 2007 in Montreal. The presentation will be on Halo 3, focusing on the in-house use of Maya along with Bungie's proprietary cinematic tools. Cowan's presentation will be on September 27th; the conference runs from the 24th to the 28th at the Hyatt Regency.