Put olive oil in a skillet on the stovetop over medium high heat.
Season all sides of tenderloin with salt and pepper. Put into skillet and sear all sides. If yours is quite thick and you want to make pulled pork to fall apart when done I would cut it in half in the middle thickest part of your meat.
Put sliced onions on bottom of Crockpot with seared tenderloin on top of that.
Sprinkle minced garlic and brown sugar on top of meat.
Whisk together in a bowl your broth, balsamic vinegar and soy sauce. Pour this on top.
Cover and cook on low for 6 hours or until the center at the thickest part reaches 145 degrees F.
If you want to make gravy to serve with it then remove meat, allow to rest before slicing, and pour liquids into a saucepan.
Allow to bubble. Take some liquid out into a cup and whisk in 2 tbsp of cornstarch. Add this back in and stir. Allow to thicken and serve together.