So epic. The number of artists and the skill level each one requires to produce this amount of work and far more than we see is exceptional. Only to aspire to!
As far as I remember Halo VFX were done in Mr X which was sister company of MPC and now merged in to it. May be because of the different pipeline and Creatives the quality looks below par.
MPC making a last reel before the Wave of AI in VFX will swoop them. Most of the shots while yes looking advanced and complex (thanks to underpaid artist for free overtime), have weird feel, almost as rendered in unreal engine.