A guide on the Immortal Achievement/Trophy for Modern Warfare 2 Remastered.
1/5/2020 - Can also confirm restarting the mission via the pause menu doesn't void it. I dd all the missions in one sitting and restarted when I died. I ended up doing S.S.D.D again as I was doing the BX achievement beforehand. Think I forgot to restart the mission after getting it.
For this you don't need to do all the mission in one go. You can do each mission via mission select on Recruit difficulty. I tested it myself on PS4 and was able to get the Platinum.
There are some things you'll want to take note of though...
Shooting General Shepard at the start, shooting your teammates and civilians etc will revert to last checkpoint.
Other sections of the campaign you need to be aware of is the jump you have to make at the end of The Hornet's Nest. The breaches you have to do on the mission. The Only Easy Day... Was Yesterday, killing the civilians will revert to last checkpoint. Also in the last breach of this mission there are explosive barrels with C4 on them. Don't shoot those as that will revert to last checkpoint.
For Exodus don't get run over by the APC, I got ran over a few times getting distracted.
In the mission Just Like Old Times when you do the breach make sure you don't shoot the C4. Also make sure you escape on time.
The biggest problem I found was rushing ahead would get me killed even on Recruit as the melee attacks from the enemies is insane especially from behind. Also the enemy grenades are still powerful on Recruit.
Overall not that hard really, I wouldn't recommend doing this straight away if you haven't played the campaign in a while.
If you're still struggling, feel free to use the time stamps below to go over the door breaches and the Jump at the end of The Hornet's Nest.
The Hornet's Nest
The Jump at the end of The Hornet's Nest.
The Only Easy Day... Was Yesterday
Last breach of level with C4 barrels.
Of Their Own Accord
The Enemy Of My Enemy
Just Like Old Times
Breach at end of level with explosives
I have this pre downloaded on the Xbox, so planning to go through it again when it comes out.