Of all of my OCs, these are the pairs that will fight the most often:

Alene and Sabel
(Though it's often one-sided from Alene's side)
Selska and Uhygg
(The two really hate eachother)
Kama and Dharati
(Same with these two)
Alene and Karah
(Alene can't stand Karah's carefree attitude. Karah finds Alene a pain in the ass.)
Sabel and Karah
(The two hold glaring contests, almost always won by Sabel.)
Karah and Kama
(Because Karah loves Dharati, she can't stand Kama)
Stoje and Nysge
(No-one really knows why, but the two just don't get along.)
Milan and Sabel
(Milan is actually a lot like Sabel, so their personalities clash. Neither of them wants to lose to the other, and that's why they fight)
Alex and Karah
(Though when Alex comes out, she will only talk to 2Ps, she always ends up fighting with Karah (and destroying some things))

These fights can include disagreements, arguments, debates, fistfights, etc.
People who almost never get into fights are:

Maria
(She's too upbeat and happy most of the time)
Thomas
(Too lazy)
Sæl
(He's just pure)
Kamm
(He agrees with what Maria thinks, and Maria doesn't really get into fights, so he doesn't either)
Mildne
(She's very patient)
Sten
(She doesn't care)

These people will fight you, regardless of if they fight often or not:

Sabel
(Don't listen to her, she'll change her mind eventually. However, she does hold grudges.
Alene
(Alene takes everything to heart, and will fight you if she feels attacked)
Mildne
(Say one wrong word about the others and you're dead)
Karah
(Insult her, you're dead. She doesn't take shit from nobody)
Uhygg
(Often just for shits and giggles, please ignore her)