I've started playing through Halo MCC on Legendary right after E3 again. I've only ever finished the first two games campaigns.
I forgot how incredibly shitty the checkpoint system in the original was. I'm only a few levels in but multiple times already I've been given a checkpoint where I'm surrounded by like 5 grunts and 4 elites lol.
I've played through all the campaigns on legendary, except Halo 2.
I doubt I will ever finish that game in my lifetime.
It's just too damn hard.
People say Ninja Gaiden and Devil May Cry are hard games on their highest difficulties. I can tell you I haven't played a harder game than Halo 2 on Legendary.