can I make a npc attack another npc on sight if its a certain class or faction? is it possible? maybe with MWSE?

Yes, my little boy did it by modifying the Dragon's Breech practice dummy script. So it is possible without MWSE.

How do you do it then?

You could make a faction (faction A) that has -128 faction reaction towards the faction(s) (faction B) you wish for the NPC to attack, and make that the faction of your attacker NPC. I think that will make all NPCs of faction A attack any member of faction B on sight.

As for class, I don't think you can do that in standard scripting.

Nope, class can't be done without some fancy extended scripting.

If you're going for a faction method, though, make sure you keep the fight values on the NPCs relatively high, but not high enough they attack the PC. You want them to be on edge, essentially.

can you set this with a script? also, it would be on a companion. Does that effect anything?