I obliterated everything in the level and it unlocked, left not a single destroyable target in the entire level.
The key I find is to use time saving techniques. The charge shot is needed to clear long lines of enemies and mines. Use the boost to move quickly and engage enemies when they become spaced apart to save time. When the wolves hide behind cover with their missile launchers, the charge shot goes through the cover if you can't line the regular shots up on them in time.
Miles Prower is the best, and he doesn't have to take crap from you.