Total War: Warhammer III

Okay so with Shadows of Change they finally added Immortal Empire Achievements which aren't actually as daunting as they first seem.

The achievements unlock after doing Ultimate Victory ... which is 272 settlements -ETA Countless hours

OR

upon defeating the end-game Crisis - ETA An hour? Maybe?

Set your Campaign Difficulty to Very Hard
Battle Difficulty to Easy
AI Stat Modifier as Low as it'll go
Turn End Game difficulty down to its lowest setting and to happen as soon as possible
Depending on which campaign you're doing
select 1 of these 2 Crisis Factions
Black Pyramid
Will of Hashut

For Pyramid all you have to do is destroy the Sentinels Faction and Occupy the Black Pyramid of Nagash
For Hashut destroy the faction that occupies Zharr Naggrund when the crisis triggers and Occupy Zharr Naggrund

and thats it Campaign done,
Pick the Legendary lords that are closest to the end game you've selected, Occupy your starting province and recruit at EVERY opportunity, even though the Crisis is on its easiest setting, Goblins vs Chorfs dont mix well
Eg. For Empire Select Volkmar and rush the pyramid
for Wood Elves go Dhurthu and use the World Roots to travel to the Oreon Forest near the Black Pyramid

The only factions I felt the Hashut Crisis was better were Greenskins, Dark Elves and Chaos Dwarfs, the rest I went pyramids