In a large pot of boiling water, add the 12 ounces of spaghetti and let them cook for about 8 to 10 minutes. As the spaghetti is cooking take the two peeled avocados and place them in a large bowl. Take a fork and begin to smash them. Add the lemon juice and olive oil and continue mix/mash the avocados until it becomes an avocado sauce-like substance. Drain the spaghetti once it has been cooked and add the avocado sauce to it and mix. Chop the tomato and add it to the pasta, along with the corn. Season with black pepper and salt to taste and serve!