I'm here to shank and smile!

FEBRUARY
TDM
  × Top-level
  × Angel
AC
- VIDEO - live from the Vault House -
February Log Top-Level

MARCH
THREADS
  Day 65: Zer0
  Rhys
  Angel
  Vault House

APRIL
THREADS
  Day 11: Zer0
   Zer0

2020
JANUARY
01: 21st Match // Video // Island 4
01: Wedding Toplevel
28: Timothy Lawrence

FEBRUARY
13: Maya
14: Hank

MARCH
01: Angel
15: Shiro
20: Maya
21: Curry Festival Top Level

APRIL
13: Armin

MAY
11: Armin
29: Shiro
29: Shadowmaru

From the wiki:

Krieg suffers from Dissociative Identity Disorder (DID). He argues with himself in some of his quotes, and he has a quieter 'inner voice' which occasionally tells him what to do or comments on his surroundings.

[...]

Krieg's inner voice is compared to a man driving an out-of-control semi truck by [Borderlands' lead writer]. He cannot stop the truck, but he can try and steer it away from as many innocents as possible.

It's hinted by Krieg's inner voice that Krieg hasn't always have DID, and so it's assumed that whatever caused it happened during his time with Hyperion. He also has trauma-related amnesia, and possesses only very vague memories of his life before Pandora.

Krieg's dominant personality is pretty clearly his violent side, as is evidenced by his typical interactions with the Borderlands world. He's far more lucid within the constraints of his own mind than he's able translate into language and action.

His peaceful side keeps his violent side in check by threatening to take control and commit suicide the instant he harms an innocent person. The arrangement appears to have worked out, because not only did Krieg survive all of the various, exciting events that transpired throughout the story in Borderlands 2, he thrived.

Positive interaction with other people is a huge benefit to Krieg. All it took was the kindness of A pretty lady with a heart of gold (cw for violence and blood) to get him started on the Path To Redemption, or at least on the Path of Not Killing People Who Don't Deserve It. We're still not sure about the former, but as of the start of BL2, we do know Krieg is definitely on the latter.

He's particularly close to Maya, but he works well with all of the vault hunters. Being able to focus on a concrete goal - in this instance, stop Handsome Jack from opening the Vault - and working toward meeting that goal is greatly beneficial to his psyche. His inner side is very aware that the way their mind works currently is not right, and that it hasn't always been this way, and holds out hope that someday they'll be able to - in his words - act like a normal person again. He believes that Maya's kindness is the starting point to their road to recovery.

Krieg plays surprisingly well with others given his generally violent nature. While he doesn't really like to listen to his inner voice, overall he absolutely prefers company, and teamwork, to being alone. Supporting team members is so important to him, in fact, that one of his skill tree branches is actually dedicated strictly to teammate revival. Redeem the Soul allows Krieg to swap places with a dying team member, granting that character an instant revival while Krieg goes down instead. "MONSTER DOWN! ANGEL UP!" is one of his lines when activating this skill.

In addition to swearing never to harm an innocent, Krieg will step in to prevent someone else harming an innocent...most likely using his own body as a meat shield. He's not squeamish in the least, and is in fact very much a masochist. His inner voice seems to believe that he deserves to suffer whatever physical pain is inflicted on him, and his outer personality actually, literally revels when he's injured. Krieg's style of combat in the context of Borderlands' gameplay is - for all intents and purposes - suicidal. Based on how skill points are distributed by the player, he receives massive stat and combat bonuses when he's injured. The lower his HP, the better the bonuses.

Snippets of monologue throughout the story reveal vague memories - mostly consisting of helping people and getting paid with loot (such as a vault hunter might do), but Krieg never allows himself to actively search for these memories, shying away from them and avoid them completely instead. His more peaceful, lucid side has some desire to remember, but his dominant, violent side does not, and he actively stops himself from attempting to recall. Despite this, he is occasionally motivated by memories of a mysterious woman - "Where is she? Is she still alive? Did she get away?" "Get up. She might still be out there." The identity of this woman (or possibly women) is never revealed, but a popular fan theory is that Krieg is the father of one of BL2's main character NPCs, Tiny Tina, and that his rare references to this woman mean either Tina, Tina's mother, or possibly both. Another possibility is that "she" could refer to Dr. Samuels, the woman in charge of Hyperion's slag experiments. Whether Krieg wants to find her to kill her or to save her is impossible to say, although she was performing her slag experiments under coercion - An Echo recording during the game's main quest reveals Handsome Jack threatening to kill her wife if she didn't perform the experiments he required. She managed to get a (somewhat garbled) apology delivered to Krieg at the end of the Son of Crawmerax DLC side quest.

He's prone to wild mood swings, and when he's feeling particularly strongly about something, he tends to spout word salad - that is, the things he says while feeling especially angry or particularly happy (for example) don't always make sense. He can get quite wordy when his emotions are dialed up to 11, which can make interpreting his meaning (if, indeed, there is any to be had at all) difficult. When he's feeling calmer he's far less talkative, but communicates far more clearly.

To conclude: Krieg knows he's a monster. It's not something he believes, it's something he accepts as a fact. Despite this (or perhaps because of it) he always puts the happiness and safety of others before his own. If left to his own devices, he would likely revert back to the crazed, blood-thirsty psychopath from his pre-BL2 days. His peaceful side definitely doesn't want that to happen, and, after building friendships with a few people, his violent side feels the same. In an RP setting, he's likely to attach himself to another person or people with a strong personality and at least reasonably decent morals (such as Maya). He may suffer from a loss of touch with reality from time to time, but he actually has a surprisingly good moral compass - his sense of "right and wrong" works just fine.