Never heard of a pacifist Pokemon before.

[Why is that a thing.]

I can think of a couple solutions, but they both seem like a pain in the ass. You might be able to switch it out for one that likes fighting at the start of a battle, but that wastes a turn and I don't even know if you can make something level up that way. The other way is figuring out why it hates fighting in the first place, but that might take even longer.