As the karma values of spells and rituals have already been listed here, I think I could post the karma values (non zero) of all the guards for reference.
Negative or positive karma from guards is 'refunded' by disbanding them, but not if they are defeated. So if you want maximum karma for the campaign at the end of a shard, disband all -karma guards and hire +karma ones everywhere.

Karma -3:
Host of the Dead
*Army of Chaos

Karma -2:
Gang of Thieves
Cutthroats
*Mob
Walking Dead
Dark Brotherhood
Battlemages
Horde
Supreme Dark Order

Karma -1:
Tribe
Secret Agents
Overseers
*Clan of Giants
*Clan of Cyclopes
*Ogres
*Trolls
(*Robbers)
(*Inquisition)
(*Medusas)

Karma +1:
Guards
Patrolmen
Guardsmen
Winged Guards
Dwarven Clan
Imperial Guards
(Halflings)

Karma +2:
Brethren of Light
Eagle Brotherhood
Forest Spirits
Forest Keepers
White Shield Order
Druid Brotherhood

Karma +3:
War Priests
Warriors of Light
Heavenly Guards
(*Forest Guards)

Edit:
() = only by diplomacy
* = cannot disband

Thanks a lot for this!

Thanks for the list.
Breeding Ground guards are neutral? I would expect them to lower Karma, with all that eating people and stuff. :-)
And why are some of the guards in brackets?

Yes, they are neutral. I put guards you can't hire in brackets. You can only get them through diplomacy and I don't know if that counts as "hiring" for karma purposes.

- Done.

- You can already attack non-dismissable guards using the plunder province button.

Wow thanks didn't realize that. I have never really used the Plunder feature except ounce very early so never realized this.