Fully Body Haki or Aura is the main counter for elemental fruit users like Venom, and it has a great ability to use against high-level players. Here's how to get it and work on leveling it up.
FASTEST way to get a FULL BODY HAKI in Blox Fruits (Roblox)
To get Full Body Haki in Blox Fruits, you need to talk to the Ability Teacher and then level him up to the max to be able to use his abilities. You need to start by going to the Frozen Village.
You can find the Ability Teacher on the Frozen Village island in the First Sea. Luckily, the First Sea is available to beginners and players up to level 700. You can find the Frozen Village on the southeast side of the sea, between the Colosseum and the Underwater City. It is a snowy island, so it should be bright enough to catch your attention if you are sailing.
When you arrive at the Frozen Village, you can find the master in the right corner of the island in a cave opening. Interact with the teacher and click on the Enhancement of Aura skill option. Pay a fee of 25,000 Beli and you can learn the skill.