Going through all the MCC campaigns legendary solo. Halo 3 is an absolute breeze after completing CE and especially 2. Like, it's almost as if I am playing on heroic, deathless runs are actually happening. On the other hand, Halo 2 Gravemind felt like I was playing the Halo version of Edge of Tomorrow. But damn, if it isn't teeth grinding and fist clenching good fun. That final fight against Tartarus, WHEN WILL HE DIE! Also, the Flood are a hell of a lot more scary in 2 than they are in 3. It's also the first time that I said 'fuck it' on Quarantine Zone and actually ran the gauntlet as far as I could in the Spectre, and it actually worked.
Sort of torn on the Flood. Sometimes I can't stand them at all, especially if they are wielding rockets. But on the other hand, there's something exhilarating about kiting a bunch of Flood with your shotgun while your ammo counter steadily declines and they just keep coming at you.
Also, the three way fights are always awesome to watch and that's what I definitely missed in Halo 4. The Prometheans first went to town on Jul's forces, but then they started working together.. I actually hope the Forerunner forces in Halo 5 consider everything a threat, not just humans.