"Halo 4: I Get a Woman!" - Sgt. Mjr. A.J. Johnson, RIP

[=sw=warlord]

Still doubt its the Didact. He was merciless, not evil.

He was the embodiment of rage.
Not only has one Halo ring been destroyed, the Ark has been destroyed as well as the replacement ring was destroyed, oh and he killed his own wife by activating the array.
I would imagine that alone would make him rather pissed off.