"Not fight anything? You had to defeat an end boss in both Fallout AND Fallout 2 to complete the game."
Fallout-
1.) Kill the master with weapons, i.e. .223 pistol, plasma rifle, super sledge hammer, etc.
2.) Sneak past the supermutants to the nuclear bomb on the 4th level of the Vault-Tec Vault. Blow it up.
3.) Talk to the Master about his plan. With a high speech, you can convince him that his plan is very flawed. Seeing the error of his ways, he kills himself.
Fallout 2-
1.) Kill Frank horrigan with weapons.
2.) Sneak past Frank Horrigan, open the door, leave. As long as combat isn't triggered, the door should open. I've never tested this, but I've heard it works.
3.) Using a high speech skill, you can talk Sargent Granite and his men in to fighting Frank for you. With the help of the turrets in the room, they can bring Frank down without you having to help.