For each Interval/Score achievement you will need to maximize your points gain. This is easier without a partner as your individual score is needed to earn this achievement. Interval 02 isn't much different from most other intervals, use cover with slow-motion (or possession) and get headshots. You can earn 5 to 6 weapon challenges here (Strader, SMG, CAS, Frag/Flash, Schuller, Goliath). Near the end you'll face off against a Powered Armor, use the Rocket Launchers in the buildings to kill it, or use Shock Grenades to stun it and then kill it with your guns. At the end of the Interval you'll fight a Phase Caster; you can continuously kill off his summoned soldiers for a higher kill bonus and a chance at more weapon challenges.