Minecraft wiki entry for Multiplayer_PvP_bases, associated text: 5. Keep improving- No base is completely unable to be raided. Even the anti-hybrid quadra thick obsidian water lava base. If someone finds a way and raids you, evolve. Block this path they found. Keep doing that, and eventually, you will have an almost unable to be raided base. Keep in mind that the wither boss can penetrate all blocks EVEN obsidian and water (with blue skulls, and spawn and death explosion and dash attack in Bedrock Edition) making the only cheap defense regenerating cobblestone walls, but hybrid cannons can penetrate those, so it will be hard to wither proof your base.