Cut peeled eggs in half horizontally and scoop egg yolks into a bowl. Scoop avocado from peels and mash the flesh into egg yolks. Stir onion and garlic into yolk mixture; add lime juice, mayonnaise, and salt. Stir until creamy.

Spoon about 1 tablespoon avocado filling into hollow of each egg white half. Place eggs onto a serving platter and sprinkle each deviled egg with a pinch of chili powder. Sprinkle Cheddar cheese over each appetizer and top each with 2 slices of olive. Cover and chill for 1 hour before serving.