Place salted butter, lime juice, lemon juice, cajun spice blend, and the peeled and deveined shrimp in a large zippered bag. Squish around to make sure everything is well combined, and then let the shrimp marinate for minimum 30 minutes up to an hour.
In a large skillet over medium high heat, cook the shrimp on each side until opaque, slightly pink and cooked through, about 1-2 minutes on each side. Set shrimp aside to cool while you prepare the guacamole.
To make the guacamole, mix the mashed avocados, green chili sauce, lime juice, lemon juice, salt, onion powder, cumin, and lemon pepper. Mix thoroughly.