Farkas gives you a quests to start a fist fight with certain NPCs, Sylgja in Shor's Stone is one of them but you can also marry her
i'm wondering if there is any adverse effects from completing Farkas's quest before you marry her or if after you marry her if she can still be targted
Best Answer
No, there are no negative impications. People who you win against in fist fights usually rather admire you for winning against them.
In principle, negative outcomes of one quest for a NPC will not affect future quests. For example, if you side with the Stormcloaks and win the war, all the Jarls defeated will gather in Solitude. While they will normally snarl at you if you visit them there, you can still finish quests given by them, and they will become happy and friendly if the outcome of the quest is in their favor.