In a small bowl, mix the onion with the lime juice.
Let stand for 10 minutes.
In a separate and much larger bowl, add the shrimp, tomatoes, cucumber, jalapeños, salt and pepper. Mix to combine and set aside.
You can add more jalapeños, if you like it spicier.
To the onions, add the tomato juice, ketchup, and hot pepper sauce.
With a fork, whisk to combine.
Then add the tomato-onion mixture to the shrimp bowl.
Stir to combine.
Add the cilantro and avocados.
Gently mix everything.
Note: You can also top off the serving with the avocado instead of adding it to the mixture.
Cover and chill for at least 1 hour.