This must be a joke. You don’t write anti-cheat in a local script, you can very easily destroy it without Dex (And checking it can also be destroyed.). Everything that is client sided is what a script injector has access to.
Then again, the average Dex & Infinite Yield user is also running malware, so we can’t assume they know anything about anything. But for that edge case where they do know what they’re doing, just use a part instanced on the server to create a forever hitbox, which can be checked effectively.