In a medium pot heat oil over medium heat. Add garlic and onions and saute until onions are translucent, 2 to 3 minutes.
Add chili powder, paprika, pepper flakes, cayenne, cumin and coriander. Saute, stirring constantly, for 2 additional minutes.
Add chicken, stir and mash with wooden spoon to break into fine pieces. cook until evenly browned, 5 to 7 minutes.
Stir in lentils, broth, tomatoes, oregano, salt, sugar and pepper. Bring to boil, then reduce heat to simmer. Cover. Stir occasionally; cook until lentils are tender and chili is think, about 30 minutes. Add more broth if lentils absorb all liquid.