Destroy All Humans Path of the Furon

Just a tip for the final boss of this level. Fire a few Disintegrator ray shots then pause time. Use temporal fist (LT and Y) directing a shot towards the boss. This does far more damage than a regular shot.

Just play through all of the story missions. When fighting the boss at the end, use the Disintegrator to continuously chip away at his health. Stay near the back of the open area to avoid his slaps. When he goes underwater your ammo will be refilled somewhat and you will have to avoid some easy lightning arcs that he creates.