Building a God in Mortal Form

[Briton]

So my last pathfinder/starjammer session had a very interesting twist. During a battle with a boss creature, one of the PCs died via his bones getting sucked out. My other PC (we shall call him Atlas) is an oracle/gunslinger who has a spirit of a literal war god stuck in his head.

When the first PC died, Atlas felt remorse for the loss of his friend, but the god said "he was a mere pet at most, a tool at the very least". Needless to say, Atlas got mad and in his anger he tried to channel the god into his dead friend in order to bring him back. The god was angry at this and tried to do the same to Atlas. I had a battle of will saves to see who was stronger and the god barely won. So now the PC (the player loved this) is a reanimated medium in his friend's body. And the god has full control over the original body.

Now i want this god to become the next BBEG (or in this case, BBNG since he was Chaotic neutral), but i need to generate a sheet for him. Do people have ideas how I would do this?

[Gildedragon]

Chaotic Wat Deity?
Barbarian with War and Chaos domain casting.
If open to 3.5 make them a runescarred berserker. Can use those 18 spells, if not at will x3 a day

[Arutema]

Now i want this god to become the next BBEG (or in this case, BBNG since he was Chaotic neutral), but i need to generate a sheet for him. Do people have ideas how I would do this?

Pathfinder handles statting out semi-divine entities via the mythic rules subsystem. Typically, demigods are MR 10 (as high as the system goes) while true deities are beyond even that and not statted.

But you're the GM, so it's up to you how much of his divine power he has in his current body. So choose how many levels and mythic ranks you give him according to when you want the campaign to end.

Storywise, if guns are a relatively new thing in the setting as PF tends to assume, a war god now controlling a gunslinger's body may be fascinated by the potential of this new weapon and its ability to pierce most armor. Maybe he'll adopt the pistol/musket as his favored weapon and now you're PCs are fighting a cult of gunfighters who worship him.