Dice the chicken breast into small, uniform bite-sized pieces.
In a medium bowl, toss the chicken with the chili powder, cumin, garlic powder, and sea salt until evenly coated.
Heat the olive oil in a non-stick skillet over medium-high heat.
Add the chicken to the skillet and cook for 6-8 minutes, stirring occasionally, until the edges are golden brown and the meat is cooked through.
While the chicken cooks, mash the avocado in a small bowl with the Greek yogurt and lime juice until the texture is smooth and velvety.
Finely dice the red onion, chop the fresh cilantro, and thinly slice the radishes.
Warm the corn tortillas in a separate dry pan over medium heat for 30 seconds per side until soft and pliable.
Assemble the tacos by dividing the chicken among the three tortillas, topping each with a dollop of avocado crema, red onion, cilantro, and radish slices.