Cut eggs lengthwise in half. Remove yolks, reserving whites. Mash yolks. Stir in 1 teaspoon minced garlic from the pepperoncini jar and 2 teaspoons pepperoncini juice. Add 3 tablespoons minced pepperoncini and the whole avocado; mash with a fork until smooth. Stir in 2 teaspoons cilantro, salt and pepper., Cut a small hole in the tip of a pastry bag or in a corner of a food-safe plastic bag; insert a medium star tip. Transfer avocado mixture to bag. Pipe into egg whites, swirling it upward to resemble Christmas trees. Sprinkle trees with minced red pepper, chili powder and remaining cilantro., Cut open and seed one larger pepperoncini; slice into 12 small diamond shapes to top Christmas trees. Refrigerate, covered, until serving. Save remaining pepperoncini for another use.