In an extra-large stockpot or Dutch oven, combine the water and beef broth if using. Bring to a boil over medium-high heat. Season with Creole Cajun seasoning, Old Bay seasoning, and hot sauce. Add onion and lemon wedges. Boil for about 15 minutes.
Add sliced andouille sausage and baby potatoes to the pot. Stir well and simmer for about 15–20 minutes until the potatoes are nearly fork-tender.
Gently add snow crab clusters, jumbo shrimp, and sweet corn to the pot. Stir carefully and boil for another 5–7 minutes until the shrimp turns pink.
In a small saucepan, melt unsalted butter with minced garlic, lemon juice, Old Bay seasoning, parsley, Creole Cajun seasoning, smoked paprika, and hot sauce. Stir continuously until well combined, about 5–7 minutes.
Prepare a baking sheet lined with foil or parchment paper. Remove contents from the pot onto the prepared surface. Pour garlic butter sauce over the seafood and toss to coat.
Serve the Cajun Seafood Boil as-is from the baking sheet or spoon portions onto individual plates. Add extra lemon wedges for squeezing on top.