Stubbs the Zombie in Rebel Without a Pulse

Not a solution but some tips from my experience on this - farming the start of level 3 with the three prisoners is by far the quickest way to obtain this. (every 20 brains = 1%)
I strongly recommend doing this when you have 2-3 hours spare and knocking this out in one sitting. (restarting the level instead of loading checkpoint is recommending to limit crashes) credit : JeremyHBPhD
I was having problems with the tracker locking up and not progressing - I believe and it's only my opinion that if you back out to the main menu or shut the console down, it does not save all of your progress.

For example, if your stuck @ 75% like I was, it is possible that you will have to eat another 1504 brains for it to start registering on the tracker again, at least that is what happened to me.

Good luck.

Edit 12/04/21 : It's been suggested that by completing the level and backing out at the start of the next level saves your progress. Maybe worth doing this if your game crashes frequently. - Thanks xxxIsaiahxxx for this additional tip.

Achievement Requisite - You must eat 2005 brains

You can eat brains when the enemy has been weakened enough. The button prompt will show up on the screen to advise that you can grab the victim and eat their brain. The screen will flash white to notify you of a brain successfully eaten.

By far the easiest difficulty to complete this challenge on is "easy", this will allow you to tank most enemies and slash your way to brain-eating. (If you are interested in enemy HP, see the bottom of this guide :) )

This achievement can be done over the course of multiple playthroughs as the achievement is accumulative. I would advise playing through the game casually once and sparing no one from brain-eating. Chances are this is the last achievement you need thus meaning you have at least completed the game 3 times (Casual Play, Fast Zombies, and Stubbs Otaku). If not, you have no need to worry.
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*METHOD 1*- Mostly Safe

The safest way to go about getting this achievement is to set aside time in your day to play through the game from start to finish in one sitting, if this is your first playthrough it will net you approx 20-30% of the way there (IF you make sure to eat everyone's brain), this one is a GRIND.. Completing the game in one sitting is the best way to avoid achievement-staggering glitches such as your counter percentage getting stuck (This can still happen but is less likely)

**IF your game crashes, just load it back up and press continue, starting a new game after a crash CAN stop the tracker**
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*METHOD 2* - Risky

If you would like to get through this grind the fastest way, the best way of doing it is by loading up mission 3 "The Slammer" and simply eating the first 3 prisoners repeatedly.

**Make sure to press RESTART LEVEL rather than restart from the last checkpoint to ensure that the tracker saves progress as much as possible.** credit : JeremyHBPhD

The issue with this method is that the tracker can break very easily if the EXACT same people are eaten repeatedly in a short amount of time. IF your tracker gets stuck and stops progressing, you WILL have to start eating 2005 brains all over again (Why this happens is unknown), so if you had eaten 1000 brains, you will need to eat 1000 again for the tracker to continue progressing.

**If your tracker gets stuck with this method (like mine), you MUST complete the rest of the "Slammer" mission and eat a few people on the next mission
credit : Its Dan**

After eating a couple you MUST start a new game completely and revert to *METHOD 1* until it starts progressing again. (Eating more of the same prisoners' brains is less likely to count and can break the tracker more, the game will stop seeing them as victims)
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**NOTE** On the final boss fight, you can brain farm the civilians that spawn in the rooms behind as they don't count as the same people, HOWEVER, DO NOT USE THE CHECKPOINT OR RESTART SYSTEM, just keep running back and forth between the rooms (If you die, do not keep farming and complete the game)


For some help and general speediness, I will outline how many attacks each NPC will take until they are grabbable (Note* some of Stubbs' random attacks will reduce the number of hits by 1, especially the uppercut, the hits outlined will be 'usual' amount)

*EASY DIFFICULTY*

Civilian - Grabbed instantly

Beat Cop - 2 Hits

Detective Cop - 3 Hits

Musket Militia - 2 Hits

Shotgun Militia - 3 Hits

White Coat Scientist - 2 Hits

Push Gun Scientist - 2 Hits

Green Coat Scientist - 2-3 Hits

Red Beret Soldier - 3 Hits

Green Hat Solider - 3 Hits

Barber Shop Quartet - 4-5 Hits

GOOD LUCK Y'ALL, I tried my best the keep this brief but any chance to avoid the glitchy suffering of this achievement is worth the read! :)