I've been focusing on getting Kokoro's bad endings today. As a result, I've been recording how to get the bad endings, so I'll post a walkthrough here now of my own Bad Ending Walkthrough.
As a note for Kokoro's route, I've learned that there's several invisible counters that pile up, such as a "Mayuzumi Stress Counter". By performing certain actions that irritate Mayuzumi too much, it raises the Stress Counter. The only way to get Bad Endings 4 and 7 is to raise this Stress Counter too high (in #7) or too low (in #4).
Spoiler for Remember11 Bad Ending Walkthrough:
Kokoro's Bad Endings:
1. Satoru Dead In The Bathroom Ending (Day 2)
Don't take the pills given to you by Utsumi. (Day 1)
2. Satoru Stabbed To Death After a Transfer End (Day 2)
Get "Killed by the Mysterious Shadow End" from Satoru's Route, then save it to your system data.
3. Genocide of the SPHIA Residents End (Day 4)
Get "Utsumi's Plan's Execution End" from Satoru's Route, then save it to your system data.
4. Annihilation End (Mayuzumi 1) (Day 4)
Apologize (Day 1)
Just keep quiet (Day 2)
Stop Yomogi (Day 2)
Explain the situation to Mayuzumi (Day 3)
Let him do the palm reading (Day 3)
Lend Yomogi a hand. (Day 3)
Say that it's okay like this. (Day 3)
Mayuzumi's argument has its good points as well. (Day 4)
I want to leave it to Mayuzumi. (Day 4)
Ask Yuni why he'd run away. (Day 4)
5. Incident At SPHIA End (Day 3)
Walk away from the building (Day 3)
Go forward (Day 3)
6. Stabbed To Death In The Bathroom End A. (Day 3)
Approach Satoru's room from the right. (Day 3)
7. Annihilation End (Mayuzumi 2) (Day 5)
Press her harder about her relationship with Satoru. (Day 1)
Voice my objection (Day 2)
Warn Mayuzumi (Day 2)
Ignore Mayuzumi (Day 3)
Tell him to try reading Mayuzumi's palm (Day 3)
I'll try asking her about her relationship with Satoru (Day 3)
I'm curious about Satoru's message (Day 3)
Make the fire hotter (Day 3)
I think Yomogi is right. (Day 4)
Ask Yuni why he'd run away (Day 4)
Entrust Yomogi with the food (Day 4)
Push Mayuzumi away (Day 5)
8. Annihilation End (Yomogi) (Day 5)
Apologize (Day 1)
Just keep quiet (Day 2)
Stop Yomogi (Day 2)
Explain the situation to Mayuzumi (Day 3)
Let him do the palm reading (Day 3)
Lend Yomogi a hand. (Day 3)
Say that it's okay like this. (Day 3)
Mayuzumi's argument has its good points as well. (Day 4)
I want to leave it to Mayuzumi (Day 4)
Run back to the cabin (Day 4)
Entrust Yomogi with the food (Day 4)
Let Yomogi handle it (Day 5)
9. Poisoned Food End (Day 5)
I ate (Day 3)
10. Death Before Reaching The Crash Site End (Day 5)
Entrust Yomogi with the food (Day 4)
At any rate, I have to move (Day 5)
11. Annihilation Ending (Mayuzumi 3) (Day 5)
I'll safeguard it. (Day 4)
"We're not like you!" (Day 5)
Was it Mayuzumi-san? (Day 5)
Fight her (Day 5)
12. Died Without Returning End (Day 5)
Entrust Yomogi with the food (Day 4)
Carry Yuni (Day 5)
13. Roaming Around The Crash Site End (Day 5)
Run away with Mayuzumi. (Day 5)
14. Kokoro Crushed by Guilt; Suicide End (Day 6)
I'll safeguard it (Day 4)
"This is the three of ours combined!" (Day 5)
Was it Mayuzumi-san? (Day 5)
Leave Yomogi behind. (Day 5)
Continue watching (Day 5)
15. Kokoro Falls Over The Cornice End (Day 7)
Turn back (Day 7)
Reach out to Yomogi (Day 7)
16. Location X Avalanche End (Day 7)
Turn back (Day 7)
Stay there and watch (Day 7)
17. Alone in the Shelter Cabin, Disaster End (Day 7)
Get "YUKIDOH's Plan's Failure End" from Satoru's route, then save it to the system data.
Satoru's Bad Endings:
18. Satoru Murdered in the Bathroom End B (Day 1)
Get "Satoru Dead in the Bathroom Ending" from Kokoro's route, then save it to the system data.
IMPORTANT NOTE! If you got this ending the first time playing through Satoru's route, then there's no way to continue any further. The only way to continue is by playing Kokoro's route all over again and getting to her Good Ending. Only then can the game continue.
19. Murdered by the Mysterious Shadow End (Day 2)
Stand my ground (Day 2)
20. Utsumi's Plan's Execution End (Day 4)
Answer "I was thirsty too" (Day 4)
21. Annihilation End B (Mayuzumi 1)
Get "Annihilation End (Mayuzumi 1)" from Kokoro's route, then save it to the system data.
22. Satoru Freezes End (Day 4)
Get "Incident at SPHIA End" from Kokoro's route, then save it to the system data.
23. Stabbed to Death in the Bathroom End B (Day 4)
Get "Stabbed to Death in the Bathroom End A" from Kokoro's route, then save it to the system data.
24. Annihilation End B (Mayuzumi 2) (Day 5)
Get "Annihilation End (Mayuzumi 2)" from Kokoro's route, then save it to the system data.
25. Genocide of the Mountain Shelter Refugees End (Day 5)
Get "Annihilation End (Yomogi)" from Kokoro's route, then save it to the system data.
26. Blood Vessels Burst End (Day 5)
Get "Poisoned Food End" from Kokoro's route, then save it to the system data.
27. Utsumi on a Rampage, Satoru Stabbed End (Day 6)
Jump onto Utsumi's back (Day 6)
28. YUKIDOH's Plan's Failure End (Day 7)
Open it (Day 7)
29. Peace of Mind, Alone in the Shelter Cabin End (Day 7)
Get "Kokoro Falls from the Cornice End" from Kokoro's route, then save it to the system data.
30. Annihilation End (Kokoro) (Day 7)
Get "Kokoro Crushed by Guilt; Suicide End" from Kokoro's route, then save it to the system data.
I'll keep updating as I get more.
EDIT: The guide is complete.