Use a pizza cutter or knife to cut the corn tortillas into thin strips. In a nonstick pan with a couple tablespoons of oil, over medium/high heat, pan fry the tortilla strips until crispy. Set aside.
In the same nonstick pan, if large, or a large pot, add a couple tablespoons oil over medium heat. Saute the onion and bell pepper for a couple minutes, until they begin to soften. Add the garlic, chili powder, cayenne, and a little salt and pepper and cook another couple of minutes.
Drain the beans and corn from the can and add to the pot. Add the chopped chipotle pepper and don't be afraid to add a little of the adobo sauce as well.
Add the stock and cook another 6-8 minutes until everything is very hot. Then stir in the cilantro. Taste, and add more salt and pepper or spice to the soup.
When you are ready to serve, add the tortilla strips to the soup and garnish as you please.
Notes
If you want more heat, you can add another chipotle pepper and/or more adobo sauce, or more cayenne. But like salt, I prefer to start lighter and add as I go since it's difficult to go back once you've made something too spicy (or too salty).