In Killzone 3, in singleplayer, destroy all chasing SawBlade APC's in the Senlin Beach section.
Chapter 3 “Pyrrhus Evac”– Senlin Beach, shortly after Mopping Up trophy, you’ll go up a highway and 2 Helghan APCs appear on your right (or left if you’re looking backwards). Destroy them and another 2 (depending on difficulty) appear immediately after them. Destroying the last 2 will spawn 1 or 2 APCs from another path on your left. Keep tapping that R1 button for the Shell Cannon which is very effective here.
Your vehicle moves on again and overtakes the ally vehicle beside you, but keep your sights facing the back as the last 2 APCs will appear behind your ally. Take them out as well, a total of 6-7 APCs, for the trophy.
If you reach the part where a Tank appears before you, you’ve missed the section.