Mission 15 - Guardians
Partway through the level you will reach a section where you must destroy many energy cores which are large blue balls with moving rings around them. You must destroy two within a 5 second window, and it is recommended that you do it using the first one you encounter and the next one up the hill to the left of that one. Kill all of the nearby enemies, and damage them until they are red. Now split up your team into 2 groups, and coordinate them to be destroyed at the same time. If you are in co-op, just time in, but if you are doing it solo, command the AI to destroy the core and immediately destroy the yours as the other one is destroyed. If you fail, reload the checkpoint.
Use a ground pound on the core to also unlock:
The Icy Cool achievement in Halo 5: Guardians worth 31 pointsUse a Ground Pound on an exterior power core in Guardians on Heroic difficulty.