C-12 shaped charge

The UNSC C-12 Shaped-charges or C-12 SCs are used mainly for heavy demolitions and can also be used as weapons. This compound is extremely dangerous and very volatile. A small 4x4x4 inch cube alone can level a five story building. It's solid, but malleable enough where it can be shaped into different forms to stick to surfaces better, and is detonated with electro-shock detonator sticks or remote detonators.

C-12 is also hefted in medium sized backpacks called "Damage Packs" or "Blow Packs". Two Damage Packs contain enough C-12 to blow through three meters of UNSC standard armor plating.

Trivia

 * In the present there is a very effective explosive called C-4 possibly a precuser