In a previous post I described how the paladin lost his shit killing a man in cold blood.

There's a Tl;dr at the bottom

After carrying their fallen friend back to the City. They are now in the local cathedral trying to resurrect the body it can keep itself alive while they find his soul.

Paladin: Cleric, is there anyway I can assist?

Cleric: I doubt so, but don't worry I and the priests will do whatever we can. Don't forget he is my friend too and these priests here owe him a grave debt. They will do whatever they can.

Paladin: Then I would like a moment alone.

Paladin: I walk away and find a prayer room.

Me: After a short walk you find an empty prayer room. With a heavy wooden door with old iron fittings. The door creaks open and you look into the small damp room. Its only source of light is a single beam of light which falls in through the small window.

Ranger: Hehe godrays

Paladin: I place my sword in the one of the crevasses in the floor and kneel behind it still holding the handle with one hand and I call out to (Let's just call him TM).

Paladin: TM please listen. I know you saw what happened and I'm deeply ashamed of what I have done.

Paladin: I place my holy symbol in the windowsill.

Paladin: TM I failed you. After so many years of loyal service I faltered. The fear of losing a dear friend to an evil man proved too much to handle. When I took my oath I wished to bring the wicked to justice and I still do, but I cannot face my failure every time I call upon your power. I will continue to bring justice and mediate peace, but I refuse to smear your name with my failure. I am not worthy to carry the blessing you gave me! So please. Take back the gift you gave me. So I can't bring further shame. What I did can never be redeemed.

Me: are you sure about this?

Paladin: Very

Me: Your holy symbol rusts in the windowsill then slowly fades away into light and as it does this you can feel the divine powers drain form you.

Paladin: I stand up.

Me: As you rise from the prayer room floor as dense mist begins to rise from in between the dull grey tiles.

Everyone else: OH SHIT!

S Paladin: So you've finally decided to ditch that useless god have you.

Paladin: You will stay out of this spectre it is none of your business.

S Paladin: I AM YOU! Of course it concerns me.

Paladin: TM granted me power and I used that power to do justice. For that reason I consider him a friend as long as I have lived.

S Paladin: A power he simply took away now that you are in dire need of it, Doesn't sound like a friend to me.

Paladin: I asked him to!

S Paladin: If a friend of yours asked you to leave him to die while you had the power to save him would you do as he asked.

Paladin: .... I would if asked.

S Paladin: Liar! I remember you dragging that ranger out of the crumbling Lich's lair. Despite him tell you to leave him. You risked your ass to safe him. All that god has to do is grant power he is in no way threatened, yet he left without so much as goodbye.

Paladin: If you are me you should know why!

S Paladin: Because he only cares about getting more followers.

Paladin: Fuck off!

Me: The mist like entity becomes a dark ash like color and picks up the sword you knelt at.

S Paladin: Perhaps I should make you see sense.

Paladin: I reach into the bag of holding and pull out the Sentry Great Axe.

Paladin: Perhaps I should just kill you here and be done with it.

Me: Ok Roll initiative.

Ranger: Wait is he fighting himself?

Cleric: In a sense I guess.

The two fight for a 2 turns.

Paladin: I cast Staggering Smite.

Me: Uh...

S Paladin: You can't even fight without that "friend" of yours how will you ever save the friend you murdered!

Paladin:...

S Paladin: You are to weak to see what I am saying.

Paladin: I ... Would like to Rage

Everyone except Pally goes wide eyed. (For this next part you should know that I briefly discussed allowing him to respec as a Barbarian if he lost his Paladin Class for good.)

Me: Your eyes begin to burn as you raise your Great Axe above your head and pound your chest.

S Paladin: You see it now, don't you!? There are other ways to deal true justice.

The paladin rolls for an attack and crits dealing significant damage.

S Paladin: You can't kill me. Not because you don't want to, but because I am part of you. From now on I will help you see what you must do.

Barbarian: The hell you will!

Barbarian: I lift up my axe and slam it into him.

Me: Before the axe strikes the spectre it disperses and the mist siphons back into you. You feel different, angrier more driven to deal out justice aside from that you feel a part of you that has felt empty for as long as you remember return.

Barbarian: I'm going to need a new outfit and stats.

Cleric: Did you just fight yourself and win?

Ranger: Not by a longshot judging by that shit eating grin on the DM's face.

Tl; dr: Paladin willingly gives up his powers and becomes a barbarian when he tries to kill himself.