I've been trying to find away to make the npc hostile after dialogue with the player. I keep getting confused at some point when I try to use the template of another npc and change of the dialogue and add a few functions.

This script in the final block of one of Col. Autumn's dialog gets him to do just what you seek. From MQ11.

Choice: I'm going to enjoy killing you.
Response: You're in over your head, I'm afraid.

Dialog embedded Script (End):
set ColonelAutumnRef.MQ11Combat to 1 <-- Look at Col. Autumn's NPC script for more on this one.
ColonelAutumnRef.StartCombat Player <-- This one starts a fight.

Other scripts off the top of my head...

The random wastelanders who are searching for Oasis will attack you after the dialog ends.

Talon Company or Regulators will attack after a conversation on your first meeting.

I don't remember if the random wastelander ghouls who couldn't get to Underworld will attack you if you pick the last "gimme your stuff" option.

depending on what you want you could also use forceFlee:

"A useful side effect of this function is that calling it with no parameters on an actor who is engaged in conversation
will immediately end the conversation, causing both participants to resume their normal packages. " (from GECK wiki)

i used a script from a quest npc